#include <bits/stdc++.h>
using namespace std;
int main() {
  string S;
  int j = 0, m = 0, f = 0, i = 0, l = 0, a = 0, p = 0, n = 0, d = 0, s = 0,
      z = 0;
  cin >> S;
  int N;
  N = S.size();
  for (int k = 0; k < 2; k++) {
    if (S.find("Olya") != -1) {
      n++;
      a = S.find("Olya");
      S[a] = '*';
    }
    if (S.find("Nikita") != -1) {
      n++;
      p = S.find("Nikita");
      S[p] = '*';
    }
    if (S.find("Danil") != -1) {
      n++;
      s = S.find("Danil");
      S[s] = '*';
    }
    if (S.find("Ann") != -1) {
      n++;
      d = S.find("Ann");
      S[d] = '*';
    }
    if (S.find("Slava") != -1) {
      n++;
      z = S.find("Slava");
      S[z] = '*';
    }
  }
  if (n == 1)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
