#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;
signed main(){
  string s;
  bool usi=true;
  getline(cin,s);
  for(int i=0;s[i]!=0;i++){
    if(i%2==0){
      if('a'>s[i]||s[i]>'z'){
        usi = false;
        break;
      }
    }else{
      if(s[i]!=' '){
        usi=false;
        break;
      }
    }
  }
  if(usi){
    cout <<"Yes\n";
  }else{
    cout <<"No\n";
  }
}