function [a,b]=gauss2(a,b)
n=length(b);
for k=1:n-1
   max=a(k,k);
   l=k;
   for i=k+1:n
       if abs(a(i,k))>max
         max=abs(a(i,k));
         l=i;
       end
   end
   l
    if(l~=k)
        for j=k:n
        auxl=a(l,j);
        a(l,j)=a(k,j);
        a(k,j)=auxl;
        end
        auxb=b(l);
        b(l)=b(k);
        b(k)=auxb;
    end
for i=k+1:n
    mult=a(i,k)/a(k,k);
    a(i,k)=0.0;
    for j=k+1:n
        a(i,j)= a(i,j) - mult*a(k,j);
    end
    b(i)=b(i)-mult*b(k);
end
a,b
k
end
return