/* -*- coding: utf-8 -*-
 *
 * 3706.cc:  No.3706 Unbroken Text - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* main */

int main() {
  char cs0[4], cs1[4];
  scanf("%s%s", cs0, cs1);

  if (abs(cs1[0] - cs0[0]) == 1) puts("Yes");
  else puts("No");

  return 0;
}