#include <bits/stdc++.h>
using namespace std;
int main() {
  string arr[5] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  string s;
  cin >> s;
  bool flag = true;
  int cnt = 0;
  for (int i = 0; i < 5; i++) {
    int p = s.find(arr[i]);
    if (p != -1) {
      if (cnt == 1) {
        flag = false;
        break;
      }
      int range = p + arr[i].size();
      int repeat = s.substr(range, s.size()).find(arr[i]);
      if (repeat != -1) {
        flag = false;
        break;
      }
      cnt++;
    }
  }
  if (flag == true && cnt == 1)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
