[求助] fortran数组越界求助，谢谢

  program main
    implicit none 
    real a
    dimension a(3,4)
    print*,"请输入增广矩阵:"
    read(*,*) a
    call gs(3,a)
    pause
    end
    subroutine gs(n,m)
  !n为线性方程组元数,m为初始增广矩阵.
implicit none
integer i,j,k,p,n
real max,m,t,x,s,l
dimension x(n),m(n,n+1),l(n,n+1)!m为初始增广矩阵，l 为化简消去过程中的增广矩阵
do k=1,n
     !选主元 
     max=abs(m(k,k))
     do i=k+1,n
         if(abs(m(i,k))>=max)then
             max=abs(m(i,k))
             p=i
         endif
     enddo
     if(p/=k)then
      !交换增广矩阵的第k行和第p行
         do j=k,n+1
            t=m(k,j)
            m(k,j)=m(p,j)
            m(p,j)=t
         enddo
     endif
     !矩阵化简
     if(k<=n) then
    do  i=k+1,n
    l(i,k)=m(i,k)/m(k,k)
    do j=k,n+1
        m(i,j)=m(i,j)-l(i,k)*m(k,j)
        enddo
    enddo
     endif
enddo
continue
!回代
x(n)=m(n,n+1)/m(n,n)
do i=n-1,1,-1
     s=m(i,n+1)
     do j=i+1,n
      s=s-x(j)*m(i,j)
     enddo
     x(i)=s/m(i,i)
end do
    do i=1,n
    write(*,10) x(i)
10  format(1x,f5.2)    
    enddo
    return
end