#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  map<string, int> names{
      {"Danil", 0}, {"Olya", 0}, {"Slava", 0}, {"Ann", 0}, {"Nikita", 0}};
  string s;
  cin >> s;
  int times = 0;
  for (auto &i : names) {
    auto found = -1;
    while (s.find(i.first, found + 1) != string::npos) {
      i.second++;
      found = s.find(i.first, found + 1);
    }
  }
  for (auto &i : names) times += i.second;
  if (times == 1)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
