#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int count = 0;
  int nPos = s.find("Danil", 0);
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Danil", nPos + 1);
  }
  nPos = s.find("Olya", 0);
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Olya", nPos + 1);
  }
  nPos = s.find("Slava", 0);
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Slava", nPos + 1);
  }
  nPos = s.find("Ann", 0);
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Ann", nPos + 1);
  }
  nPos = s.find("Nikita", 0);
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Nikita", nPos + 1);
  }
  if (count == 1) {
    cout << "YES";
  } else {
    cout << "NO";
  }
}
