#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using pint=pair<int,int>;
#define rep(i,n) for(int i=0;i<(n);++i)
template<typename T>
void chmax(T& a,T b){if(a<b){a=b;};}
template<typename T>
void chmin(T& a,T b){if(a>b){a=b;};}
const int inf=1e9;

int main(){
  char c1,c2;cin>>c1>>c2;
  if(c1+1==c2||c1-1==c2)cout<<"Yes\n";
  else cout<<"No\n";
}