#include <bits/stdc++.h>
using namespace std;
const int N = 1e5;
map<string, bool> mp;
int main() {
  int cnt = 0;
  string s;
  cin >> s;
  mp["Danil"] = mp["Olya"] = mp["Slava"] = mp["Ann"] = mp["Nikita"] = true;
  for (int i = 0; i < s.size(); i++) {
    string t = "";
    for (int j = 0; j < 6; j++) {
      if (i + j >= s.size()) break;
      t += s[i + j];
      if (mp[t]) cnt++;
    }
  }
  if (cnt == 1) return cout << "YES", 0;
  cout << "NO";
  return 0;
}
