#include <bits/stdc++.h>
using namespace std;
const long long Llinf = LLONG_MAX;
const int Inf = INT_MAX;
const int Maxn = 1e3 + 10;
const int Mod = 1e9 + 7;
char* _c = new char[Maxn];
string GetString() {
  scanf("%s", _c);
  return string(_c);
}
string s;
string t[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
int ans;
int Check(string s, string t) {
  int ret = 0;
  for (int i = 0; i < s.size(); i++)
    if (s.substr(i, t.size()) == t) ret++;
  return ret;
}
int main() {
  s = GetString();
  for (int i = 0; i < 5; i++) ans += Check(s, t[i]);
  if (ans == 1)
    printf("YES\n");
  else
    printf("NO\n");
  return 0;
}
