#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, s1 = "Danil", s2 = "Olya", s3 = "Slava", s4 = "Ann", s5 = "Nikita";
  cin >> s;
  long long l = 0;
  for (long long i = 0; i < s.size(); i++) {
    string c1 = s.substr(i, 5);
    if (c1 == s1) l++;
    string c2 = s.substr(i, 4);
    if (c2 == s2) l++;
    string c3 = s.substr(i, 5);
    if (c3 == s3) l++;
    string c4 = s.substr(i, 3);
    if (c4 == s4) l++;
    string c5 = s.substr(i, 6);
    if (c5 == s5) l++;
  }
  l == 1 ? cout << "Yes" : cout << "No";
}
