#include <bits/stdc++.h>
using namespace std;
using ll=long long;
const int INF=1e9;

int main() {
	cin.tie(nullptr),cout.tie(nullptr);
	ios::sync_with_stdio(false);
  
  char a,b;
  cin >> a >> b;
  
  int x=a-'A';
  int y=b-'A';
  if(abs(x-y)==1){
    cout << "Yes" << endl;
    return 0;
  }
  
    cout << "No" << endl;
}