#include <bits/stdc++.h>
using namespace std;
const long long int mod = 1000000000 + 7;
const long long int N = 10000000 + 6;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  string check[5] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  string st;
  cin >> st;
  int n = st.size();
  int c = 0;
  for (int j = 0; j < 5; j++) {
    int pos = 0;
    int index;
    while ((index = st.find(check[j], pos)) != string::npos) {
      c++;
      pos = index + 1;
    }
  }
  if (c != 1)
    cout << "NO";
  else
    cout << "YES";
  return 0;
}
