#include <bits/stdc++.h>
using namespace std;
int main() {
  string str;
  cin >> str;
  int t = 0;
  string a, b, c, d, e;
  for (int i = 0; i < str.length(); i++) {
    a = str.substr(i, 5);
    if (a == "Danil") t = t + 1;
    b = str.substr(i, 4);
    if (b == "Olya") t = t + 1;
    c = str.substr(i, 5);
    if (c == "Slava") t = t + 1;
    d = str.substr(i, 3);
    if (d == "Ann") t = t + 1;
    e = str.substr(i, 6);
    if (e == "Nikita") t = t + 1;
  }
  if (t == 1)
    cout << "YES";
  else
    cout << "NO";
}
