#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  string a[5] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  int count = 0;
  for (int i = 0; i < (5); ++i) {
    size_t flag = s.find(a[i]);
    if (flag != string::npos) {
      count++;
      string p = s.substr(flag + a[i].length());
      flag = p.find(a[i]);
      if (flag != string::npos) count++;
    }
  }
  if (count != 1)
    cout << "NO";
  else
    cout << "YES";
  return 0;
}
