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