#include <bits/stdc++.h>
using namespace std;
int main(void) {
  string second[5] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  int sum = 0;
  string t;
  cin >> t;
  for (int i = 0; i < 5; i++) {
    int pos = t.find(second[i], 0);
    while (pos != string::npos) {
      sum++;
      pos = t.find(second[i], pos + 1);
    }
  }
  if (sum == 1)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}
