import java.util.*;
public class Main {
   public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);

      String S = sc.next();
      char c = S.charAt(0);

      S = "abcdefghijklmnopqrstuvwxyz";
      char[] a = new char[26];
      for (int i = 0; i < a.length; i++) {
         a[i] = S.charAt(i);
      }

      char cb = a[0];

      for (int i = 0; i < a.length-1; i++) {
         if(c == a[i]){
            cb = a[i+1];
         }
      }

      System.out.println(cb);

   }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz