#include <bits/stdc++.h>
using namespace std;
const int MAX = (int)1e5 + 55;
const int INF = (int)1e9 + 77;
const int MOD = (int)1e9 + 7;
const double PI = 2 * acos(0.0);
const double EPS = 1e-7;
string s[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
string str;
int count(int j) {
  int ret = 0;
  for (int i = 0; i <= (int)str.length() - (int)s[j].size(); ++i) {
    int k = 0;
    for (; k < s[j].length(); k++)
      if (s[j][k] != str[i + k]) break;
    if (k == s[j].size()) ++ret;
  }
  return ret;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> str;
  int ans = 0;
  for (int i = 0; i < 5; ++i) ans += count(i);
  if (ans == 1)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
