RT，不知道哪里常数大了过不去

#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
ull a[32], ans;
ull yh[32];
int f(ull x)
{
   int cnt = 0;
   while(x>>=1)++cnt;
   return cnt;
}
int main()
{
   ios::sync_with_stdio(0);
   int n; cin >> n;
   for(int i = 0; i < n; ++i)
      cin >> a[i];
   for(ull S = 1; S < 1ull<<n; ++S)
   {
      ull lb = S&-S;
      int cnt = f(lb);
      if(!(S&(S-1)))
      {
         yh[cnt] = a[cnt];
         ans ^= S*yh[cnt];
      }
      else
      {
         lb ^= S;
         ull lb2 = lb&-lb;
         int c2 = f(lb2);
         yh[cnt] = yh[c2]^a[cnt];
         ans ^= S*yh[cnt];
      }
   }
   cout << ans << '\n';
   return 0;
}