#include <bits/stdc++.h>
using namespace std;
bool check(string str, string name, int ind) {
  if (ind + name.size() > str.size()) {
    return 0;
  }
  for (int i = ind, j = 0; j < name.size(); i++, j++) {
    if (str[i] != name[j]) {
      return 0;
    }
  }
  return 1;
}
int main() {
  string str;
  cin >> str;
  int f = 0;
  for (int i = 0; i < str.size(); i++) {
    f += check(str, "Danil", i);
    f += check(str, "Olya", i);
    f += check(str, "Slava", i);
    f += check(str, "Ann", i);
    f += check(str, "Nikita", i);
  }
  if (f == 1) {
    cout << "YES\n";
  } else {
    cout << "NO\n";
  }
}
