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

int main() {
  string s;
  cin >> s;
  for(int i = 0;i < s.size();i++){
    if(i%2 == 0){
      if(s[i]-'a'+1 > 26){
        cout << "No" << endl;
        return 0;
      }
    }
    else{
      if(s[i] != ' '){
        cout << "No" << endl;
        return 0;
      }
    }
  }
  cout << "Yes" << endl;
}