#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int n = s.size();
  int br = 0;
  for (int i = 0; i < n; i++) {
    if (s.substr(i, 6) == "Nikita" || s.substr(i, 5) == "Danil" ||
        s.substr(i, 4) == "Olya" || s.substr(i, 3) == "Ann" ||
        s.substr(i, 5) == "Slava") {
      br++;
    }
  }
  if (br == 1) {
    cout << "YES" << endl;
  } else
    cout << "NO" << endl;
}
