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