#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 5;
const int MOD = 1e9 + 7;
const long long INF = 1e18 + 8;
const int maxn = 3e5 + 5;
int a[maxn], vis[maxn], su[maxn];
string str[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
string s;
int main() {
  cin >> s;
  int flag = 0;
  for (int i = 0; i < 5; i++) {
    for (int j = 0; j < s.size(); j++) {
      if (s.substr(j, str[i].size()) == str[i]) {
        flag++;
      }
    }
  }
  if (flag == 1) {
    puts("Yes\n");
  } else {
    puts("No\n");
  }
  return 0;
}
