diff --git a/Cargo.lock b/Cargo.lock
index e1c7a66..a3cba5c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -141,6 +141,12 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "either"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60b1af1c220855b6ceac025d3f6ecdd2b7c4894bfe9cd9bda4fbb4bc7c0d4cf0"
+
 [[package]]
 name = "encode_unicode"
 version = "0.3.6"
@@ -176,6 +182,7 @@ dependencies = [
  "anyhow",
  "clap",
  "dialoguer",
+ "itertools",
 ]
 
 [[package]]
@@ -184,6 +191,15 @@ version = "1.70.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7943c866cc5cd64cbc25b2e01621d07fa8eb2a1a23160ee81ce38704e97b8ecf"
 
+[[package]]
+name = "itertools"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "413ee7dfc52ee1a4949ceeb7dbc8a33f2d6c088194d9f922fb8318faf1f01186"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "lazy_static"
 version = "1.5.0"
diff --git a/Cargo.toml b/Cargo.toml
index 8251df7..47c6f61 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,3 +7,4 @@ edition = "2021"
 anyhow = "1.0.86"
 clap = { version = "4.5.17", features = ["derive"] }
 dialoguer = "0.11.0"
+itertools = "0.13.0"
diff --git a/src/atbash.rs b/src/atbash.rs
deleted file mode 100644
index 0b5c47f..0000000
--- a/src/atbash.rs
+++ /dev/null
@@ -1,34 +0,0 @@
-use crate::util;
-
-pub struct AtabashChipher {
-    alphabet: Vec<char>,
-}
-
-impl AtabashChipher {
-    pub fn new(alphabet: &str) -> anyhow::Result<Self> {
-        let alphabet = alphabet.chars().collect::<Vec<_>>();
-
-        util::verify_alphabet(&alphabet)?;
-
-        Ok(Self { alphabet })
-    }
-
-    pub fn encode(&self, input: &str) -> anyhow::Result<String> {
-        let mut output = String::with_capacity(input.len());
-
-        for c in input.chars() {
-            let index = self
-                .alphabet
-                .iter()
-                .position(|&x| x == c)
-                .ok_or(anyhow::anyhow!("cannot encode character {:?}", c))?;
-            output.push(self.alphabet[self.alphabet.len() - index - 1]);
-        }
-
-        Ok(output)
-    }
-
-    pub fn decode(&self, input: &str) -> anyhow::Result<String> {
-        self.encode(input)
-    }
-}
diff --git a/src/caesar.rs b/src/caesar.rs
deleted file mode 100644
index daee3ce..0000000
--- a/src/caesar.rs
+++ /dev/null
@@ -1,56 +0,0 @@
-use crate::util;
-
-pub struct CaesarCipher {
-    alphabet: Vec<char>,
-    offset: i64,
-}
-
-impl CaesarCipher {
-    pub fn new(alphabet: &str, offset: i64) -> anyhow::Result<Self> {
-        let alphabet = alphabet.chars().collect::<Vec<_>>();
-        let offset = offset % alphabet.len() as i64;
-
-        util::verify_alphabet(&alphabet)?;
-
-        Ok(Self { alphabet, offset })
-    }
-
-    pub fn encode(&self, input: &str) -> anyhow::Result<String> {
-        let mut output = String::with_capacity(input.len());
-
-        for c in input.chars() {
-            let index = self.get_index(c, self.offset)?;
-            output.push(self.alphabet[index])
-        }
-
-        Ok(output)
-    }
-
-    pub fn decode(&self, input: &str) -> anyhow::Result<String> {
-        let mut output = String::with_capacity(input.len());
-
-        for c in input.chars() {
-            let index = self.get_index(c, -self.offset)?;
-            output.push(self.alphabet[index])
-        }
-
-        Ok(output)
-    }
-
-    fn get_index(&self, c: char, offset: i64) -> anyhow::Result<usize> {
-        let mut index =
-            self.alphabet
-                .iter()
-                .position(|&x| x == c)
-                .ok_or(anyhow::anyhow!("cannot encode character {:?}", c))? as i64
-                + offset;
-
-        while index < 0 {
-            index += self.alphabet.len() as i64;
-        }
-
-        index %= self.alphabet.len() as i64;
-
-        Ok(index as usize)
-    }
-}
diff --git a/src/main.rs b/src/main.rs
index 57b2ded..f766104 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,78 +1,68 @@
-use clap::Parser;
+use itertools::Itertools;
 
-mod atbash;
-#[allow(dead_code)]
-mod caesar;
-#[allow(dead_code)]
-mod polybius_square;
 mod util;
 
-#[derive(Debug, clap::Parser)]
-struct Args {
-    #[clap(subcommand)]
-    command: Command,
-}
-
-#[derive(Debug, clap::Subcommand)]
-enum Command {
-    User,
-    Cli {
-        #[clap(short, long)]
-        mode: Mode,
-        #[clap(short, long)]
-        input: String,
-        #[clap(short, long)]
-        alphabet: String,
-    },
-}
-
-#[derive(Debug, Clone, clap::ValueEnum)]
-enum Mode {
-    Encode,
-    Decode,
-}
-
-fn main() -> anyhow::Result<()> {
-    let args = Args::parse();
-
-    match args.command {
-        Command::User => {
-            let alphabet = dialoguer::Input::<String>::new()
-                .with_prompt("Enter alphabet")
-                .with_initial_text("АаБбВвГгДдЕеЁёЖжЗзИиЙйКкЛлМмНнОоПпРрСсТтУуФфХхЦцЧчШшЩщЪъЫыЬьЭэЮюЯя0123456789 ,.:!?_-+/*='^%#&@$")
-                .validate_with(|input: &String| {
-                    let chars = input.chars().collect::<Vec<_>>();
-                    util::verify_alphabet(&chars)
-                })
-                .interact_text()?;
-            let input = dialoguer::Input::<String>::new()
-                .with_prompt("Enter input")
-                .interact_text()?;
-
-            let atbash = atbash::AtabashChipher::new(&alphabet)?;
-
-            let encoded = atbash.encode(&input)?;
-            println!("Result: {}", encoded);
-        }
-        Command::Cli {
-            mode,
-            input,
-            alphabet,
-        } => {
-            let atbash = atbash::AtabashChipher::new(&alphabet)?;
-
-            match mode {
-                Mode::Encode => {
-                    let encoded = atbash.encode(&input)?;
-                    println!("{}", encoded);
-                }
-                Mode::Decode => {
-                    let decoded = atbash.decode(&input)?;
-                    println!("{}", decoded);
-                }
-            }
+fn encode(group_size: usize, filler_char: char, input: String) -> String {
+    let mut input = util::remove_whitespace(util::remove_punctuation(input));
+    let len = input.chars().count();
+    if len % group_size != 0 {
+        for _ in 0..(group_size - len % group_size) {
+            input.push(filler_char);
         }
     }
 
+    let mut result = String::new();
+    for chunk in &input.chars().rev().chunks(group_size) {
+        for c in chunk {
+            result.push(c);
+        }
+        result.push(' ');
+    }
+
+    result
+}
+
+fn decode(_group_size: usize, filler_char: char, input: String) -> String {
+    let result = util::remove_whitespace(util::remove_punctuation(input))
+        .chars()
+        .rev()
+        .collect::<String>();
+
+    result.trim_end_matches(filler_char).to_string()
+}
+
+fn main() -> anyhow::Result<()> {
+    let group_size = dialoguer::Input::<usize>::new()
+        .with_prompt("Enter group size")
+        .validate_with(|input: &usize| {
+            if input > &1 {
+                Ok(())
+            } else {
+                Err("Must be greater than 1".to_string())
+            }
+        })
+        .interact_text()?;
+    let filler_char = dialoguer::Input::<char>::new()
+        .with_prompt("Filler character")
+        .default('A')
+        .interact_text()?;
+    let input = dialoguer::Input::<String>::new()
+        .with_prompt("Enter input")
+        .interact_text()?;
+    let mode = dialoguer::Select::new()
+        .with_prompt("Mode")
+        .item("Encode")
+        .item("Decode")
+        .default(0)
+        .interact()?;
+
+    let result = match mode {
+        0 => encode(group_size, filler_char, input),
+        1 => decode(group_size, filler_char, input),
+        _ => unreachable!(),
+    };
+
+    println!("Result: {}", result);
+
     Ok(())
 }
diff --git a/src/polybius_square.rs b/src/polybius_square.rs
deleted file mode 100644
index 8e0471f..0000000
--- a/src/polybius_square.rs
+++ /dev/null
@@ -1,69 +0,0 @@
-use crate::util;
-
-pub struct PolybiusSquareCipher {
-    alphabet: Vec<char>,
-    rows: usize,
-    columns: usize,
-}
-
-impl PolybiusSquareCipher {
-    pub fn new(alphabet: &str, columns: usize, rows: usize) -> anyhow::Result<Self> {
-        let alphabet = alphabet.chars().collect::<Vec<_>>();
-        util::verify_alphabet(&alphabet)?;
-        if rows * columns != alphabet.len() {
-            return Err(anyhow::anyhow!(
-                "rows * columns must equal the length of the alphabet"
-            ));
-        }
-
-        Ok(Self {
-            alphabet,
-            rows,
-            columns,
-        })
-    }
-
-    pub fn encode(&self, input: &str) -> anyhow::Result<String> {
-        let mut output = String::with_capacity(input.len());
-
-        for c in input.chars() {
-            let index = self
-                .alphabet
-                .iter()
-                .position(|&x| x == c)
-                .ok_or(anyhow::anyhow!("invalid character"))?;
-
-            let row = index / self.columns;
-            let col = index % self.columns;
-
-            output.push(self.alphabet[((row + 1) % self.rows) * self.columns + col]);
-        }
-
-        Ok(output)
-    }
-
-    pub fn decode(&self, input: &str) -> anyhow::Result<String> {
-        let mut output = String::with_capacity(input.len());
-
-        for c in input.chars() {
-            let index = self
-                .alphabet
-                .iter()
-                .position(|&x| x == c)
-                .ok_or(anyhow::anyhow!("invalid character"))?;
-
-            let mut row = index / self.columns;
-            let col = index % self.columns;
-
-            if row == 0 {
-                row = self.rows - 1;
-            } else {
-                row -= 1;
-            }
-
-            output.push(self.alphabet[(row % self.rows) * self.columns + col]);
-        }
-
-        Ok(output)
-    }
-}
diff --git a/src/util.rs b/src/util.rs
index 00c33b2..c3c1cad 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -1,17 +1,7 @@
-pub fn verify_alphabet(alphabet: &[char]) -> anyhow::Result<()> {
-    if alphabet.len() < 2 {
-        return Err(anyhow::anyhow!(
-            "Alphabet must contain at least 2 characters"
-        ));
-    }
-
-    let mut alphabet_set = std::collections::HashSet::new();
-    for c in alphabet {
-        if alphabet_set.contains(c) {
-            return Err(anyhow::anyhow!("Alphabet contains duplicate characters"));
-        }
-        alphabet_set.insert(*c);
-    }
-
-    Ok(())
+pub fn remove_whitespace(input: String) -> String {
+    input.chars().filter(|c| !c.is_whitespace()).collect()
 }
+
+pub fn remove_punctuation(input: String) -> String {
+    input.chars().filter(|c| !c.is_ascii_punctuation()).collect()
+}
\ No newline at end of file