#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int pos = 0;
  int matches = 0;
  while ((pos = s.find("Danil", pos)) <= s.length()) {
    matches++;
    pos += 5;
  }
  pos = 0;
  while ((pos = s.find("Olya", pos)) <= s.length()) {
    matches++;
    pos += 4;
  }
  pos = 0;
  while ((pos = s.find("Slava", pos)) <= s.length()) {
    matches++;
    pos += 5;
  }
  pos = 0;
  while ((pos = s.find("Ann", pos)) <= s.length()) {
    matches++;
    pos += 3;
  }
  pos = 0;
  while ((pos = s.find("Nikita", pos)) <= s.length()) {
    matches++;
    pos += 6;
  }
  if (matches == 1)
    printf("%s", "YES");
  else
    printf("%s", "NO");
}
