function x=lufelb(A,b)
  [n,m]=size(A)
  L=eye(n)
  for j=1:n-1
    for i=j+1:n
      t=A(i,j)/A(j,j)
      A(i,:)=A(i,:)-t*A(j,:)
      L(i,j)=t
    endfor
  endfor
  U=A
  y=also(L,b)
  x=felso(U,y)
endfunction