#include "math.h"
void hhbg(a,n)
int n;
double a[];
{ 
	int i,j,k,u,v;
    double d,t;
    for (k=1; k<=n-2; k++)
    { 
		d=0.0;
        for (j=k; j<=n-1; j++)
        { 
			u=j*n+k-1; t=a[u];
            if (fabs(t)>fabs(d))
            { 
				d=t; i=j;
			}
        }
        if (fabs(d)+1.0!=1.0)
        { 
			if (i!=k)
            { 
				for (j=k-1; j<=n-1; j++)
                { 
					u=i*n+j; v=k*n+j;
                    t=a[u]; a[u]=a[v]; a[v]=t;
                }
                for (j=0; j<=n-1; j++)
                { 
					u=j*n+i; v=j*n+k;
                    t=a[u]; a[u]=a[v]; a[v]=t;
                }
            }
            for (i=k+1; i<=n-1; i++)
            { 
				u=i*n+k-1; t=a[u]/d; a[u]=0.0;
                for (j=k; j<=n-1; j++)
                { 
					v=i*n+j;
                    a[v]=a[v]-t*a[k*n+j];
                }
                for (j=0; j<=n-1; j++)
                { 
					v=j*n+k;
                    a[v]=a[v]+t*a[j*n+i];
                }
            }
        }
    }
    return;
}