import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String N = sc.next();
        char C = N.charAt(0);

        String alphabetList = "abcdefghijklmnopqrstuvwxyz";

        char[] Sc = alphabetList.toCharArray();
        char ans='z';

        for(int i=0; i<Sc.length; i++){
            if(C == Sc[i] && C != 'z'){
                ans = Sc[i+1];
            }
        }

        System.out.println(ans);

    }
}


/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