#include <bits/stdc++.h>
using namespace std;
const long long INF = (1LL << 60) - 1;
int main() {
  int t = 1;
  while (t--) {
    string s;
    cin >> s;
    int n = s.size();
    map<string, int> m;
    m["Daniel"] = 1;
    m["Olya"] = 1;
    m["Slava"] = 1;
    m["Ann"] = 1;
    m["Nikita"] = 1;
    int cnt = 0;
    for (int i = 0; i < n - 2; i++) {
      string tmp = "";
      for (int j = i; j < n; j++) {
        tmp += s[j];
        if (tmp.size() > 6) {
          break;
        }
        if (tmp == "Danil" || tmp == "Olya" || tmp == "Slava" || tmp == "Ann" ||
            tmp == "Nikita") {
          cnt++;
        }
      }
    }
    if (cnt == 1)
      cout << "YES";
    else
      cout << "NO";
  }
  return 0;
}
