#include <bits/stdc++.h>
long long int MOD = 1000000007;
using namespace std;
long long int power(long long int x, long long int y, long long int p) {
  long long int res = 1;
  x = x % p;
  if (x == 0) return 0;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
bool sortbysec(const pair<long long int, long long int> &a,
               const pair<long long int, long long int> &b) {
  return (a.second < b.second);
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  long long int t;
  t = 1;
  while (t--) {
    string p;
    cin >> p;
    vector<string> vec = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
    unordered_map<string, long long int> M;
    for (long long int i = 0; i < vec.size(); i++) {
      string::size_type pos = 0;
      while ((pos = p.find(vec[i], pos)) != std::string::npos) {
        M[vec[i]]++;
        pos += vec[i].size();
      }
    }
    long long int sum = 0;
    for (auto &x : M) {
      sum += x.second;
    }
    cout << (sum == 1 ? "YES" : "NO") << endl;
  }
}
