void add(bigint x, bigint y)
{
    long i, c, n;
    c = 0;
    n = max(x[0], y[0]);
    for (i = 1; i <= n; i++) {
	x[i] += y[i] + c;
	if (x[i] >= BASE) {
	    c = 1;
	    x[i] -= BASE;
	} else {
	    c = 0;
	}
    }
    if (c > 0) x[++n] = c;
    x[0] = n;
}