long sum(long n, long a[n][n])
{
    int i, j;
    long s = 0;
    for (i = 0; i < n; i++)
        for (j = 0; j < n; j++)
            s += a[i][j];
    return s;
}
/*
long sum(long n, long a[n][n])
{
    int i, j;
    long s = 0;
    long *p = a;

    for (i = 0; i < n; i++) {
        for (j = 0; j < n; j++)
            s += p[j];

        p += n;
    }
    return s;
}

*/