function B = fattLU(A)
n=size(A,1); 
for k=1:n-1 
  A(k+1:n,k)=A(k+1:n,k)/A(k,k); 
  for j=k+1:n, 
    for s=k+1:n 
      A(s,j)=A(s,j)-A(s,k)*A(k,j) ; 
    end
  end
end
B=A;