#include <bits/stdc++.h>
using namespace std;
const long long int M = 4e3 + 5, LG = 30, inf = 1e18, mod = 1e9 + 7;
string s;
long long int f(string t) {
  long long int cnt = 0;
  for (int i = 0; i < ((long long int)s.size()) - ((long long int)t.size()) + 1;
       i++) {
    for (int j = 0; j < ((long long int)t.size()); j++) {
      if (s[i + j] != t[j]) goto here;
    }
    cnt++;
  here:
    continue;
  }
  return cnt;
}
int main() {
  ios::sync_with_stdio(0);
  cin >> s;
  long long int cnt =
      f("Danil") + f("Olya") + f("Slava") + f("Ann") + f("Nikita");
  cout << (cnt == 1 ? "YES" : "NO");
}
