#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  string s[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  string a;
  cin >> a;
  int ct = 0;
  for (int i = 0; i < 5; i++) {
    size_t nPos = a.find(s[i], 0);
    while (nPos != string::npos) {
      ct++;
      nPos = a.find(s[i], nPos + 1);
    }
  }
  if (ct == 1)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
