#include <bits/stdc++.h>
using namespace std;
int countFreq(string &pat, string &txt) {
  int M = pat.length();
  int N = txt.length();
  int res = 0;
  for (int i = 0; i <= N - M; i++) {
    int j;
    for (j = 0; j < M; j++)
      if (txt[i + j] != pat[j]) break;
    if (j == M) {
      res++;
      j = 0;
    }
  }
  return res;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n, m, i, k = 2000000000000000007, j = 2000000000000000007, q, l = 0,
                     r = 0;
  char c;
  string s;
  cin >> s;
  string s1 = "Danil", s2 = "Olya", s3 = "Slava", s4 = "Ann", s5 = "Nikita";
  l += (countFreq(s1, s));
  l += (countFreq(s2, s));
  l += (countFreq(s3, s));
  l += (countFreq(s4, s));
  l += (countFreq(s5, s));
  if (l == 1)
    cout << "YES\n";
  else
    cout << "NO\n";
}
