#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC target("sse4")
using namespace std;
template <class T>
T gcd(T a, T b) {
  return ((b == 0) ? a : gcd(b, a % b));
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  string s;
  cin >> s;
  int cnt = 0;
  set<string> st = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  for (int i = 0; i < (int)(s.size()); i++) {
    for (int j = (int)(1); j < (int)(s.size() - i + 1); j++) {
      string cur = s.substr(i, j);
      if (st.find(cur) != st.end()) cnt++;
    }
  }
  if (cnt == 1)
    cout << "YES" << '\n';
  else
    cout << "NO" << '\n';
  return 0;
}
