#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  string s;
  getline(cin, s);
  for (int i = 0; i < (int) s.size(); i++) {
    if (i % 2 == 0) {
      if ('a' > s[i] || s[i] > 'z') {
        cout << "No\n";
        return 0;
      }
    } else {
      if (s[i] != ' ') {
        cout << "No\n";
        return 0;
      }
    }
  }
  cout << "Yes\n";
  return 0;
}