#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
long long power(long long a, long long b) {
  long long ans = 1;
  while (b > 0) {
    if (b & 1) ans *= a;
    a = a * a;
    b >>= 1;
  }
  return ans;
}
long long powm(long long a, long long b) {
  a %= MOD;
  long long ans = 1;
  while (b > 0) {
    if (b & 1) ans = (ans * a) % MOD;
    a = (a * a) % MOD;
    b >>= 1;
  }
  return ans;
}
int main() {
  string s;
  cin >> s;
  vector<string> check = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  int cnt = 0, n = (int)s.size();
  for (int i = 0; i < n; i++) {
    string t;
    for (int j = i; j < n; j++) {
      t += s[j];
      if (find(check.begin(), check.end(), t) != check.end()) cnt++;
    }
  }
  if (cnt == 1)
    cout << "YES\n";
  else
    cout << "NO\n";
  return 0;
}
