#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    char a, b;
    cin >> a >> b;
    cout << (abs(a - b) == 1 ? "Yes" : "No") << endl;
    return 0;
}