#include <iostream>
#include <cassert>
using namespace std;

#define N 16  // N must be either 16 or 32

#if N==16
typedef int16_t Int;
#else
typedef int32_t Int;
#endif

int bitsum(Int n){
    // Count the one bits in n
    int count = 0;
    while (n != 0){
        count += 1;
        n &= n-1;
    }
    return count;
}

int main() {
    assert(N==16 or N==32);
#if N==16
    Int w[5];
    w[0] = 0;
    w[1] = 0x5555;
    w[2] = 0x3333;
    w[3] = 0x0f0f;
    w[4] = 0x00ff;
#else
    Int w[6];
    w[0] = 0;
    w[1] = 0x55555555;
    w[2] = 0x33333333;
    w[3] = 0x0f0f0f0f;
    w[4] = 0x00ff00ff;
    w[5] = 0x0000ffff;
#endif
    int count = 1;   // we know v = 0 works
    for (Int v = 1; v != 0; ++v) {
        if (bitsum(v)%2 != 0) continue;
        for (auto x:w) {
            if (bitsum(v^x)== N/2) {
                ++count;
                break;
            }
        }
    }
    cout << "count = " <<count << " for n = " << N << endl;
    return 0;
}