#include <bits/stdc++.h>
using namespace std;
using vi = vector<int>;
using vvi = vector<vi>;
using vs = vector<string>;
using si = set<int>;
using ull = unsigned long long;
template <typename structure>
void print(structure v) {
  for (auto e : v) cout << e << " ";
  cout << endl;
}
int main() {
  string s;
  cin >> s;
  int c = 0;
  if (s.find("Danil") != -1) c++;
  if (s.find("Olya") != -1) c++;
  if (s.find("Slava") != -1) c++;
  if (s.find("Ann") != -1) c++;
  if (s.find("Nikita") != -1) c++;
  int x = s.find("Danil");
  if (x != -1 && s.find("Danil", x + 2) != -1) {
    c++;
  }
  x = s.find("Olya");
  if (x != -1 && s.find("Olya", x + 2) != -1) {
    c++;
  }
  x = s.find("Slava");
  if (x != -1 && s.find("Slava", x + 2) != -1) c++;
  x = s.find("Ann");
  if (x != -1 && s.find("Ann", x + 2) != -1) c++;
  x = s.find("Nikita");
  if (x != -1 && s.find("Nikita", x + 3) != -1) c++;
  cout << (c == 1 ? "YES" : "NO") << endl;
  return 0;
}
