real U2(100,100), U1(100,100), U0(100,100)
!     open (10, file="laine.in")
      open (20,file="laine.out")
      read *,nt
      alpha=0.05
      nxy=100
!*****initsialiseerimine 
      do i=1,nxy
      do j=1,nxy
      U1(i,j)=0.
      U0(i,j)=0.
      enddo
      enddo
!***** alg tingimused *****
      do i=1,5
      do j=2,nxy-1
      U1(i,j)=10.
      U0(i,j)=10.
      enddo
      enddo
!**********************************************
      do k=1,nt
      
      do i=2,nxy-1
      do j=2,nxy-1
      U2(i,j)=alpha*(U1(i+1,j)-4.*U1(i,j)+U1(i-1,j)
     *+U1(i,j+1)+U1(i,j-1))+2.*U1(i,j)-U0(i,j)
      enddo
      enddo
!****** raja tingimused *********
      do i=1,nxy
      U2(i,nxy)=0.
      U2(i,1)=0.
      U2(nxy,i)=0.
      U2(1,i)=0.
      enddo
!****** salvestamine ***************
      do i=1,nxy
      do j=1,nxy
      U0(i,j)=U1(i,j)
      U1(i,j)=U2(i,j)
      enddo
      enddo
!****** kirjutamine ********
      if((k/2)*2.eq.k)then
      write(20,100) U2*10
100   Format (100F12.5)
      endif
      enddo
!***********************************************
      stop
      end