#include <bits/stdc++.h>
using namespace std;
string name[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
int coun;
void check(string s) {
  for (auto x : name) {
    if (s == x) coun++;
  }
}
int main() {
  string s;
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    string temp = "";
    for (int j = i; j < s.size(); j++) {
      temp += s[j];
      check(temp);
    }
  }
  if (coun == 1)
    puts("YES");
  else
    puts("NO");
  return 0;
}
