#include <bits/stdc++.h>
using namespace std;
long long power(long long a, long long b) {
  long long res = 1;
  a %= 1000000007;
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % 1000000007;
    a = a * a % 1000000007;
  }
  return res;
}
string a, b, c;
int q, n, t;
int arr[1000009];
int brr[1000009];
int main() {
  cin >> a;
  vector<string> vc = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  int n = a.size();
  for (int i = 0; i <= 10; i++) a += '%';
  int p = 0;
  for (int i = 0; i < vc.size(); i++) {
    string s = vc[i];
    for (int j = 0; j < n; j++)
      if (a.substr(j, s.size()) == s) p++;
  }
  if (p == 1) {
    cout << "YES";
  } else
    cout << "NO";
}
