#include <bits/stdc++.h>
using namespace std;
string ch[9] = {"Danil", "Olya", "Slava", "Ann", "Nikita"}, str;
int main() {
  int sum = 0, i, j;
  cin >> str;
  for (i = 0; i < 5; i++)
    for (j = ch[i].size() - 1; j <= str.size(); j++) {
      string s(str, j - ch[i].size() + 1, ch[i].size());
      if (s == ch[i]) sum++;
    }
  if (sum == 1)
    puts("YES");
  else
    puts("NO");
}
