#include <bits/stdc++.h>
using namespace std;
int main() {
  string name;
  string list[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  int sdafdsf = 0;
  cin >> name;
  int len = sizeof(list) / sizeof(*list);
  for (int i = 0; i < len; i++) {
    if (list[i].length() > name.length()) {
      continue;
    } else {
      size_t nPos = name.find(list[i], 0);
      while (nPos != string::npos) {
        sdafdsf++;
        if (sdafdsf > 1) {
          cout << "NO" << endl;
          exit(0);
        }
        nPos = name.find(list[i], nPos + 1);
      }
    }
  }
  if (sdafdsf == 1) {
    cout << "YES" << endl;
  } else {
    cout << "NO" << endl;
  }
  return 0;
}
