#include <bits/stdc++.h>
using namespace std;
string s;
string subs[100];
int cnt, ans;
int main() {
  cin >> s;
  for (int i = 0; i < s.length(); i++) {
    if (s[i] == '_')
      cnt++;
    else if (s[i] >= 'A' && s[i] <= 'Z') {
      subs[++cnt] += s[i];
    } else
      subs[cnt] += s[i];
  }
  for (int i = 0; i <= cnt; i++) {
    string ss;
    for (int j = 0; j < subs[i].length(); j++) {
      ss += subs[i][j];
      if (ss == "Danil" || ss == "Olya" || ss == "Slava" || ss == "Ann" ||
          ss == "Nikita") {
        ans++;
      }
    }
  }
  cout << (ans == 1 ? "YES" : "NO");
  return 0;
}
