#include <bits/stdc++.h>
using namespace std;
int main() {
  cin.tie(0), cerr.tie(0), ios_base::sync_with_stdio(0);
  string s;
  cin >> s;
  map<string, int> mp;
  mp["Danil"] = 0;
  mp["Olya"] = 0;
  mp["Slava"] = 0;
  mp["Ann"] = 0;
  mp["Nikita"] = 0;
  for (int i = 0; i < s.length(); ++i) {
    string a = "";
    for (int j = i; j < min((int)s.length(), i + 6); ++j) {
      a += s[j];
      if (mp.find(a) != mp.end()) {
        mp[a]++;
      }
    }
  }
  int sum = 0;
  for (auto it : mp) {
    sum += it.second;
  }
  if (sum == 1) {
    cout << "YES";
  } else {
    cout << "NO";
  }
  return 0;
}
