#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  string s;
  cin >> s;
  long long c = 0;
  size_t found;
  found = s.find("Danil");
  if (found != string::npos) c++;
  found = s.find("Danil", found + 1);
  if (found != string::npos) c++;
  found = s.find("Olya");
  if (found != string::npos) c++;
  found = s.find("Olya", found + 1);
  if (found != string::npos) c++;
  found = s.find("Slava");
  if (found != string::npos) c++;
  found = s.find("Slava", found + 1);
  if (found != string::npos) c++;
  found = s.find("Ann");
  if (found != string::npos) c++;
  found = s.find("Ann", found + 1);
  if (found != string::npos) c++;
  found = s.find("Nikita");
  if (found != string::npos) c++;
  found = s.find("Nikita", found + 1);
  if (found != string::npos) c++;
  if (c == 1)
    cout << "YES" << '\n';
  else
    cout << "NO" << '\n';
  return 0;
}
