#include <bits/stdc++.h>
using namespace std;
vector<string> fs;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  fs.push_back("Danil");
  fs.push_back("Olya");
  fs.push_back("Slava");
  fs.push_back("Ann");
  fs.push_back("Nikita");
  string second;
  long long int n, i, j;
  bool ansx = 1;
  long long int fx = 0;
  cin >> second;
  n = second.size();
  for (i = 0; i < fs.size(); i++) {
    for (j = 0; j < n; j++) {
      long long int u = fs[i].size();
      string s1 = second.substr(j, u);
      if (s1 == fs[i]) fx++;
    }
  }
  if (fx == 1)
    cout << "YES\n";
  else
    cout << "NO\n";
  return 0;
}
