Magicheskii kvadrat

bool magkvadrat(int** a, int n)
{
    int k,i, j;
    bool b = true;
    int sumstr, sumstlb, sumdiag = 0, sumpobdiag = 0, sum=0;
    for (j = 0; j < n; j++)
        sum = sum + a[0][j];

    for (i = 0; i < n && b; i++)
    {
        sumstr = 0;
        sumstlb = 0;
        for (j = 0; j < n; j++)
        {
            sumstr = sumstr + a[i][j];
            sumstlb = sumstlb + a[j][i];
            if (i == 0)
            {
                sumdiag = sumdiag + a[j][j];
                sumpobdiag = sumpobdiag + a[j][n - 1 - j];
            }
        }
        if (sumstr != sum || sumstlb != sum || sumdiag != sum || sumpobdiag != sum)
            b = false;
    }
    return b;
}