void mprove(double a[], double alud[], int n, int indx[], double b[], double x[])
{
	int i, j;
    const int nmax = 100;
    double r[100];
	double sdp;
    for (i = 1; i<=n; i++)
	{
        sdp = -b[i];
        for (j = 1; j<=n; j++)
		{
            sdp = sdp + a[(i-1)*n+j] * x[j];
        }
        r[i] = sdp;
    }
    lubksb(alud, n, indx, r);
    for (i = 1; i<=n; i++)
	{
        x[i] = x[i] - r[i];
    }
}