2nd

src/main.rs

@@ -2,6 +2,8 @@ fn main() {
     // In general, the `{}` will be automatically replaced with any
     // arguments. These will be stringified.
     println!("{} days", 31);
+    let s = format!("formatted {} days", 31);
+    println!("{}", s);
 
     // Without a suffix, 31 becomes an i32. You can change what type 31 is
     // by providing a suffix. The number 31i64 for example has the type i64.