#ifndef INCLUDED_MAIN
#define INCLUDED_MAIN

#include __FILE__

using namespace nskr;


int main(void){
    char a, b; cin >> a >> b;
    if(abs(a-b) == 1) cout << "Yes\n";
    else cout << "No\n";
}

#else
#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using ld=  long double;
#define rep(i,n) for(i=0;i<(n);i++)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()

namespace nskr{}

int randint(int a, int b){
    static mt19937 gen(chrono::steady_clock::now().time_since_epoch().count());
    uniform_int_distribution<int> dist(a,b);
    return dist(gen);
}


#endif