#include <bits/stdc++.h>
using namespace std;
char A[115], name[5][10] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
int cnt;
int main() {
  cin.sync_with_stdio(false);
  scanf("%s", A);
  int len = strlen(A);
  for (int i = 0; i < len; ++i) {
    for (int j = 0; j < 5; ++j) {
      bool st = true;
      int Ilen = strlen(name[j]);
      for (int k = 0; k < Ilen; ++k) {
        if (A[i + k] != name[j][k]) st = false;
      }
      if (st) cnt++;
    }
  }
  if (cnt == 1) return !printf("YES\n");
  return !printf("NO\n");
}
