#include <bits/stdc++.h>
using namespace std;
string arr[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  string s, sub;
  cin >> s;
  int cnt = 0;
  if (s.size() >= 3) {
    for (int i = 0; i < 5; i++) {
      for (int j = 0; j + arr[i].size() <= s.size(); j++) {
        sub = s.substr(j, arr[i].size());
        if (sub == arr[i]) {
          cnt++;
        }
      }
    }
  }
  if (cnt == 1)
    cout << "YES\n";
  else
    cout << "NO\n";
}
