subroutine stream(uf,vf,psi,nx,ny)
      integer i,j,nx,ny,nxm,nym,mxym
      include 'gridsz'
      double precision uf(nx,ny),vf(nx,ny),psi(0:nx,0:ny)
      double precision uby,vby,utop,ubot,h,hinv
      common/uvboud/uby(nym),vby(nym),utop,ubot
      common/meshsz/h,hinv
      do 5 i=0,nx
         psi(i,0) = 0.D0
 5    continue
      do 10 j=1,ny
         psi(0,j) = 0.D0
      do 12 i=1,nx
         psi(i,j) = psi(i,j-1) - psi(i-1,j) + psi(i-1,j-1) +
     +              2.D0*h*uf(i,j)
 12   continue
 10   continue
      write(24,*) psi
      write(24,101)
 101  format(/)
      end