#include <bits/stdc++.h>
using namespace std;
string s;
int main() {
  cin >> s;
  int cnt = 0;
  for (int i = 0; s[i]; i++) {
    string s1 = "";
    for (int l = i; s[l]; l++) {
      s1 += s[l];
      if (s1 == "Danil") {
        cnt++;
        break;
      }
      if (s1 == "Olya") {
        cnt++;
        break;
      }
      if (s1 == "Slava") {
        cnt++;
        break;
      }
      if (s1 == "Ann") {
        cnt++;
        break;
      }
      if (s1 == "Nikita") {
        cnt++;
        break;
      }
    }
  }
  if (cnt == 1)
    puts("YES");
  else
    puts("NO");
  return 0;
}
