#include "math.h"
#include "stdio.h"
int gsdl(a,b,n,x,eps)
int n;
double a[],b[],x[],eps;
{ 
	int i,j,u,v;
    double p,t,s,q;
    for (i=0; i<=n-1; i++)
    { 
		u=i*n+i; p=0.0; x[i]=0.0;
		for (j=0; j<=n-1; j++)
		{
			if (i!=j)
            { 
				v=i*n+j; 
				p=p+fabs(a[v]);
			}
			if (p>=fabs(a[u]))
			{ 
				printf("fail\n"); 
				return(-1);
			}
		}
    }
    p=eps+1.0;
    while (p>=eps)
    { 
		p=0.0;
        for (i=0; i<=n-1; i++)
        { 
			t=x[i]; s=0.0;
            for (j=0; j<=n-1; j++)
				if (j!=i) s=s+a[i*n+j]*x[j];
            x[i]=(b[i]-s)/a[i*n+i];
            q=fabs(x[i]-t)/(1.0+fabs(x[i]));
            if (q>p) p=q;
        }
    }
    return(1);
}