diff --git a/src/euler51/src/main.rs b/src/euler51/src/main.rs
index f52d0a5..62fecd8 100644
--- a/src/euler51/src/main.rs
+++ b/src/euler51/src/main.rs
@@ -12,12 +12,6 @@ type Int = u64;
 // const LENGTH: usize = 2;
 // const MIN_LENGTH: usize = 1;
 
-// OWN TEST
-// const MIN_VALUE: Int = 100;
-// const MAX_VALUE: Int = 999;
-// const LENGTH: usize = 3;
-// const MIN_LENGTH: usize = 2;
-
 // EXAMPLE 2
 // const MIN_VALUE: Int = 10_000;
 // const MAX_VALUE: Int = 99_999;
@@ -49,24 +43,26 @@ fn main() {
                 }
             }
             if primes_matching_pattern.len() > 2 {
-                best_this_combination.push(primes_matching_pattern)
+                best_this_combination.push(primes_matching_pattern);
             }
         }
         if !best_this_combination.is_empty() {
-            best_of_all_combinations.push(get_longest(best_this_combination, false));
+            best_of_all_combinations.push(get_longest(best_this_combination));
         }
     }
-    println!("{:#?}", get_longest(best_of_all_combinations, false));
+    println!("{:#?}", get_longest(best_of_all_combinations));
 }
 
 fn apply_transformation(prime_as_digits: &[u8], new_digit: u8, pattern: &[bool]) -> Int {
     debug_assert_eq!(prime_as_digits.len(), pattern.len());
     let mut multiplier = 1;
     let result = prime_as_digits
+        // apply the pattern to prime_as_digits
         .iter()
         .zip(pattern)
         .map(|(old_digit, replace)| if *replace { new_digit } else { *old_digit })
         .map(|d| d as Int)
+        // calculate Int
         .rev()
         .reduce(|accum, item| {
             multiplier *= 10;
@@ -77,13 +73,11 @@ fn apply_transformation(prime_as_digits: &[u8], new_digit: u8, pattern: &[bool])
     result
 }
 
-fn get_longest(mut vec: Vec<Vec<Int>>, print: bool) -> Vec<Int> {
-    if vec.is_empty() {
-        panic!("cannot give the longest element of an empty vector")
-    }
-    if print {
-        println!("{:#?}", vec);
-    }
+fn get_longest(mut vec: Vec<Vec<Int>>) -> Vec<Int> {
+    assert!(
+        !vec.is_empty(),
+        "cannot get the longest element of an empty vector"
+    );
     vec.sort_by_key(|c| c.len());
     let length = vec.last().unwrap().len();
     vec.into_iter().find(|v| v.len() == length).unwrap()
@@ -93,10 +87,6 @@ trait ToDigits {
     fn to_digits(&self) -> Vec<u8>;
 }
 
-trait ToNum {
-    fn to_num(&self) -> Int;
-}
-
 impl ToDigits for Int {
     fn to_digits(&self) -> Vec<u8> {
         self.to_string()
@@ -106,27 +96,9 @@ impl ToDigits for Int {
     }
 }
 
-impl ToNum for Vec<u8> {
-    fn to_num(&self) -> Int {
-        let mut result = 0;
-        let mut position = 1;
-        for digit in self.iter().rev() {
-            result += *digit as Int * position;
-            position *= 10;
-        }
-        result
-    }
-}
-
 #[cfg(test)]
 mod test {
-    use crate::{apply_transformation, ToDigits, ToNum};
-
-    #[test]
-    fn test_digits_to_num() {
-        let digits = vec![5, 7, 3, 8, 1];
-        assert_eq!(digits.to_num(), 57381);
-    }
+    use crate::{apply_transformation, ToDigits};
 
     #[test]
     fn test_num_to_digits() {