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