init for prob4 part 1

src/lib.rs

@@ -1,3 +1,4 @@
 pub mod prob1;
 pub mod prob2;
-pub mod prob3;
+pub mod prob3;
+pub mod prob4;

src/main.rs

@@ -21,6 +21,6 @@ fn main() {
     {
         let file_path = "prob3_part2.txt";
         let max_part2 = prob3::solve_part2(file_path);
-        println!("Solution for problem 3 part 1: {max_part2}");
+        println!("Solution for problem 3 part 2: {max_part2}");
     }
 }