diff --git a/agc022/src/bin/a.rs b/agc022/src/bin/a.rs
index 2a9506c8..8de0e466 100644
--- a/agc022/src/bin/a.rs
+++ b/agc022/src/bin/a.rs
@@ -1,10 +1,33 @@
-use proconio::{input, marker::Usize1};
+use proconio::{input, marker::Chars};
 
 fn main() {
     input! {
-        n: usize,
-        a: [Usize1; n],
+        s: Chars,
     };
-    let ans = n - a.len();
-    println!("{}", ans);
+    let mut used = vec![false; 26];
+    for c in s.iter().copied() {
+        used[(c as u8 - b'a') as usize] = true;
+    }
+
+    for (i, b) in used.iter().copied().enumerate() {
+        if !b {
+            print!("{}", s.into_iter().collect::<String>());
+            println!("{}", (i as u8 + b'a') as char);
+            return;
+        }
+    }
+
+    for (i, c) in s.iter().copied().enumerate().rev() {
+        for j in (c as u8) + 1..=b'z' {
+            if !used[(j - b'a') as usize] {
+                for k in 0..i {
+                    print!("{}", s[k]);
+                }
+                println!("{}", j as char);
+                return;
+            }
+        }
+        used[(c as u8 - b'a') as usize] = false;
+    }
+    println!("-1");
 }