Chia hết cho 2^k (LQDOJ)

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
using namespace std;
const int N = 2e5;
int n, k;
long long a[N+1], cnt = 0, b[65];
void read()
{
   cin >> n >> k;
   fill (b + 1, b + 65, 0);
   for (int i = 1; i <= n; ++ i)
   {
       cin >> a[i];
       int cnt = 0;
       while (a[i] % 2 == 0)
       {
           ++cnt;
           a[i]/=2;
       }
       a[i] = cnt;
       ++b[cnt];
   }
}
long long c3(long long x)
{
    return x*(x-1)*(x-2)/6;
}
long long c2 (long long x)
{
    return x*(x-1)/2;
}
void solve()
{
   for (int i = 0; i <= 64; ++ i)
   {
       for (int j = i + 1; j <= 64; ++ j)
       {
           for (int z = j + 1; z <= 64; ++ z)
           {
               if (i + j + z >= k)
               {
                   cnt += b[i] * b[j] * b[z];
               }
           }
       }
   }
   for (int i = 0; i <= 64; ++ i)
   {
       for (int j = i + 1; j <= 64; ++ j)
       {
           if (2 * i + j >= k)
           {
               cnt += c2(b[i]) * b[j];
           }
           if (i + 2 * j >= k)
           {
               cnt += b[i] * c2(b[j]);
           }
       }
   }
   for (int i = 0; i <= 64; ++ i)
   {
       if (3 * i >= k)
       {
           cnt += c3(b[i]);
       }
   }
   cout << cnt;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    read();
    solve();
}