#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, n, count = 0;
  string str, a[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  cin >> str;
  n = str.length();
  for (i = 0; i < n; i++) {
    for (j = 0; j < 5; j++) {
      if (i + a[j].length() > n) continue;
      if (str.substr(i, a[j].length()) == a[j]) count++;
    }
  }
  if (count == 1)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
