#include <bits/stdc++.h>
using namespace std;
int find(string p, string t) {
  int l2 = t.size();
  int l1 = p.size();
  int count = 0;
  for (int i = 0; i <= l1 - l2; i++) {
    int j;
    for (j = 0; j < l2; j++) {
      if (p[i + j] != t[j]) break;
    }
    if (j == l2) {
      count++;
    }
  }
  return count;
}
int main() {
  string s;
  cin >> s;
  int b1 = find(s, "Danil");
  b1 += find(s, "Olya");
  b1 += find(s, "Slava");
  b1 += find(s, "Ann");
  b1 += find(s, "Nikita");
  if (b1 == 1) {
    cout << "YES";
  } else {
    cout << "NO";
  }
}
