#include <bits/stdc++.h>
using namespace std;
int main() {
  string str[5] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  string s;
  int cnt = 0;
  cin >> s;
  for (int i = 0; i < 5; i++) {
    for (int j = 0; j < s.size(); j++) {
      if (s.substr(j, str[i].size()) == str[i]) cnt++;
    }
  }
  if (cnt == 1)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
