!     Gauss Elimination Method
      implicit none
      integer n
      parameter (n=3)
      real(8),dimension(n,n) :: a
      real(8),dimension(n)    :: b,x
      real(8) an
      integer i,j,k
       call input(a,b)
       call print(a,b)
       do i=1,n
        an=a(i,i)
         do j=i,n
          a(i,j)=a(i,j)/an
         end do
         b(i)=b(i)/an
         call print(a,b)
         do k=i+1,n
          an=a(k,i)
          do j=i,n
           a(k,j)=a(k,j)-an*a(i,j)
          end do
          b(k)=b(k)-an*b(i)
         end do
       call print(a,b)
      end do
      do i=n,1,-1
       x(i)=b(i)
       do j=i+1,n
        x(i)=x(i)-x(j)*a(i,j)
       end do
      end do
      do i=1,n
       write(*,100) i,x(i)
      end do
  100 format (1x,'Ans.','x(',i1,')=',1pe12.5)
      stop
      end
      subroutine input(a,b)
      implicit none
      integer n
      parameter (n=3)
      real(8),dimension(n,n) :: a
      real(8),dimension(n) :: b
       a(1,1)=1.0
       a(1,2)=2.0
       a(1,3)=1.0
       a(2,1)=3.0
       a(2,2)=8.0
       a(2,3)=7.0
       a(3,1)=2.0
       a(3,2)=7.0
       a(3,3)=4.0
       b(1)=3.0
       b(2)=5.0
       b(3)=8.0
      return
      end
      subroutine print(a,b)
      implicit none
      integer n
      parameter (n=3)
      real(8),dimension(n,n) :: a
      real(8),dimension(n) :: b
      integer i,j
        do i=1,n
         write(*,*) (real(a(i,j)),j=1,n),real(b(i))
        end do
      write(*,*) '-----------------'
      return
      end