diff --git a/src/lib.rs b/src/lib.rs
index 5762b5f..ed07268 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,8 +1,7 @@
-extern crate core;
-
 pub mod prob1;
 pub mod prob2;
 pub mod prob3;
 pub mod prob4;
 pub mod prob5;
-pub mod prob6;
\ No newline at end of file
+pub mod prob6;
+pub mod prob7;
diff --git a/src/prob4/mod.rs b/src/prob4/mod.rs
index 35e3b3e..f1ea45c 100644
--- a/src/prob4/mod.rs
+++ b/src/prob4/mod.rs
@@ -11,37 +11,31 @@ pub fn complete_overlap(first_pair: &[u32], second_pair: &[u32]) -> bool {
 
 pub fn solve(file_path: &str, unary_operator: &dyn Fn(&[u32], &[u32]) -> bool) -> i32 {
     std::fs::read_to_string(file_path)
-        .expect("Please provide a text file as an argument.")
+        .unwrap_or_else(|err| panic!("Please provide a text file as an argument: {err}"))
         .lines()
         .map(|line| {
             let tmp = line.split(',').collect::<Vec<&str>>();
             let first_pair = tmp
                 .first()
-                .expect("First character error")
+                .unwrap_or_else(|| panic!("First character error"))
                 .split('-')
                 .map(|first_split| {
                     first_split
                         .parse::<u32>()
-                        .expect("Parsing number in first pair failed")
+                        .unwrap_or_else(|err| panic!("Parsing number in first pair failed: {err}"))
                 })
                 .collect::<Vec<u32>>();
             let second_pair = tmp
                 .last()
-                .expect("First character error")
+                .unwrap_or_else(|| panic!("First character error"))
                 .split('-')
                 .map(|first_split| {
                     first_split
                         .parse::<u32>()
-                        .expect("Parsing number in first pair failed")
+                        .unwrap_or_else(|err| panic!("Parsing number in first pair failed: {err}"))
                 })
                 .collect::<Vec<u32>>();
-            if unary_operator(&first_pair, &second_pair) {
-                1
-            } else {
-                0
-            }
+            i32::from(unary_operator(&first_pair, &second_pair))
         })
-        .collect::<Vec<i32>>()
-        .iter()
         .sum()
 }
\ No newline at end of file