#include<iostream>
#include<math.h>
using namespace std;
void main()
{ 
 float a[3][3],b[3];
 int i,j,k,l;
 float t,d,he;
 k=0;
 he=0;
 a[3][3]=((2,-1,3),(4,2,5),(1,2,0));
 b[3]=(1,4,7);

 sub: d=a[k][k];
 l=k;
 i=k+1;
 smb:
 if(fabs(a[i][k])>fabs(d)){d=a[i][k];l=i;}
 
 else { if(i!=2) {i++;goto smb;}
      else{ 
           if(d==0) {cout<<"奇異矩陣."<<"\n";return;}
		   else{  
 	           if(l!=k) 
			   { 
		        for(j=k;j<=2;j++) { t=a[l][j];a[l][j]=a[k][j];a[k][j]=t;}
		        t=b[k];b[k]=b[l];b[l]=t;
			   }
		   
			 
                   for(j=k+1;j<=2;j++) {a[k][j]=a[k][j]/a[k][k];}
                   b[k]=b[k]/a[k][k];
                   for(i=k+1;i<=2;i++)
				   {
                     for(j=k+1;j<=2;j++)
                     a[k][j]=a[i][j]-a[i][k]*a[k][j];
                     b[i]=b[i]-a[i][k]*b[k];
				   }
			 
		   }
	  }
 }
 if(k!=2){k=k+1;goto sub;}
 else 
 {
  for(i=1;i>=0;i--) 
  { he=0;
	for(j=i+1;j<=2;j++) he=he+a[i][j]*b[j];
	b[i]=b[i]-he;
  }
 }
 for(i=0;i<=2;i++)
 cout<<"b"<<i<<"="<<b[i]<<"\n";
}