#include <bits/stdc++.h>
using namespace std;
const int maxn = 100001;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int t = 1;
  int cnt = 0;
  while (t--) {
    string s;
    cin >> s;
    string names[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
    for (int i = 0; i < 5; i++) {
      size_t nPos = s.find(names[i], 0);
      while (nPos != string::npos) {
        cnt++;
        nPos = s.find(names[i], nPos + 1);
      }
    }
  }
  if (cnt == 1) {
    cout << "YES";
    return 0;
  }
  cout << "NO";
  return 0;
}
