Add exit function

 use std::io;
 use std::io;
 
 
 fn main() {
 fn main() {
-    let mut input = String::new();
-    io::stdin().read_line(&mut input);
-    print!("{}", input);
+    loop {
+        let mut input = String::new();
+        io::stdin().read_line(&mut input);
+        if input == "exit\n" {
+            return;
+        }
+        print!("{}", input);
+    }
 }
 }