#include "stdafx.h"
#include <math.h>

int main(void)
{
 const int n=3;
 const double w=0.0001;
 double a[n][n]={{4.2,-1.7,1.3},
 {0,8.5,2.3},
 {4.5,-0.5,8.2}};
 double b[n]={2.8,-0.6,0.1};
 double x[n];

 int i,j,k;
 double c=0, D=0, norm=0;



 for(i=0;i<n;i++)
  x[i]=0;


 for(k=0; k<100; k++)
 {
  for (i=0; i<n; i++)
  {
   norm=0;
   c=b[i];
   for(j=0; j<n; j++)
   {
    if(i!=j) c=c-a[i][j]*x[j];
   }
   c=c/a[i][i];
   D=fabs(c-x[i]);
   x[i]=c;
   if(norm<D) norm=D;
  }
  printf("k=%d " , k);
  printf(" norm=%.1e " , norm);
  printf("\n");
  if(norm<w)
  {
   for(i=0;i<n;i++)
   {
    printf(" x[%d]= %f" ,i+1,x[i]);
    printf("\n");
   }
   return 0;
  }
 }
printf("ne sosholsia\n");
return 0;
}