#include <bits/stdc++.h>
using namespace std;
string str[5] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
int main() {
  string s;
  cin >> s;
  int ans = 0;
  for (int i = 0; i < 5; ++i) {
    int p = 0;
    while ((p = s.find(str[i], p) + 1) != 0) ans++;
  }
  if (ans == 1)
    printf("YES\n");
  else
    printf("NO\n");
}
