//
// Created by ree04 on 2020/10/10.
//
#include <stdio.h>

int main() {
	const char *plain = "abcdefghijklmnopqrstuvwxyz";
	char input[27] = { 0 };
	scanf("%s", input);
	int cnt;

	for (cnt = 0; input[cnt] == plain[cnt]; cnt++);

	printf("%cto%c", plain[cnt], input[cnt]);

	return 0;
}