#include <bits/stdc++.h>
using namespace std;
int main() {
  string x;
  cin >> x;
  int i, j;
  int len = x.size();
  int count = 0;
  for (i = 0; i < len; i++) {
    for (j = 1; j <= len - i; j++) {
      string z = x.substr(i, j);
      if (z == "Danil" || z == "Olya" || z == "Slava" || z == "Ann" ||
          z == "Nikita")
        count++;
    }
  }
  if (count == 1)
    cout << "Yes";
  else
    cout << "No";
}
