#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  string s;
  cin >> s;
  vector<int> cnt(26, 0);
  for (char c : s) cnt[c - 'A']++;
  cout << (*max_element(cnt.begin(), cnt.end()) == 1 ? "YES" : "NO") << endl;
  return 0;
}