#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 6, mod = 1e9 + 7, INF = 1 << 30;
int a[N], b[N], g[N], h[N];
string a1[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
int main() {
  string s;
  int ans = 0;
  cin >> s;
  for (int(i) = int(0); i < int(s.size()); i++) {
    for (int(j) = int(0); j < int(5); j++) {
      if (s.substr(i, a1[j].size()) == a1[j]) {
        ans++;
      }
    }
  }
  if (ans == 1) {
    cout << "YES";
  } else
    cout << "NO";
}
