program main
  integer*4, parameter          :: n=600, l=600, m=600
  real*8                        :: A(l,m), B(m,n), C(l,n)

  write (*,*) size(A,1)
  call init(A)
  call init(B)
  call mtx_mul(A,B,C)
  ! call prt(C)
contains
  subroutine init(mtx)
    real*8, intent(out)        :: mtx(:,:)
    integer*4                  :: i,j

    do i = 1,ubound(mtx, 1)
      do j = 1,ubound(mtx, 2)
        mtx(i,j) = (i-1)*(j-1) + 0.6 * (j-1) + 3.4;
      enddo
    enddo
  end subroutine init

  subroutine prt(mtx)
    real*8, intent(in)        :: mtx(:,:)
    integer*4                  :: i,j

    do i = 1,ubound(mtx, 1)
      do j = 1,(ubound(mtx, 2) -1)
        write (*,"(F10.1)",advance="no")  mtx(i,j)
      enddo
      write (*,"(F10.1)") mtx(i,ubound(mtx, 2))
    enddo
  end subroutine prt

  subroutine mtx_mul(A, B, C)
    real*8, intent(in)       :: A(:,:), B(:,:)
    real*8, intent(out)      :: C(:,:)
    integer*4                :: i, j, k

    C = 0d0;

    do k = 1,ubound(C,2)
      do i = 1,ubound(C,1)
        do j = 1,ubound(A,2)
          C(i,k) = C(i,k) + A(i,j) * B(j,k)
        enddo
      enddo
    enddo

  end subroutine mtx_mul

end program main