#include <bits/stdc++.h>
using namespace std;
string kek;
int l = 0;
int main() {
  string s;
  string q[11111] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  cin >> s;
  for (int i = 0; i < s.length(); i++) {
    kek = "";
    for (int j = i; j <= i + 6; j++) {
      kek += s[j];
      for (int k = 0; k < 5; k++) {
        if (kek == q[k]) {
          l++;
        }
      }
    }
  }
  if (l == 1) {
    cout << "YES" << endl;
  } else {
    cout << "NO" << endl;
  }
  return 0;
}
