real,allocatable:: tu(:,:),tv(:,:),alpha(:,:)
open(10,file="s2d3.dat")
open(20,file="s2d3_last.dat")
nx=100
allocate(tu(nx,nx),tv(nx,nx),alpha(nx,nx))

!**** algtingimused ****
tu=0.
tv=0.
alpha=0.01

nt=40000
do it=1,nt

do i=2,nx-1 
do j=2,nx-1

if (.not.(i.le.80.and.j.ge.40.and.j.le.50)) then
tu(i,j)=tv(i,j)+alpha(i,j)*(tv(i+1,j)-4.*tv(i,j)+tv(i-1,j)+tv(i,j+1)+tv(i,j-1))
endif

enddo
enddo

tu(1:20,nx)=500.
tu(1:20,1)=100
tu(nx,1:20)=100.

tu(20:nx,nx)=tu(20:nx,nx-1)
tu(20:nx,1)=tu(20:nx,2)
tu(1,:)=tu(2,:)
tu(nx,20:nx)=tu(nx-1,20:nx)

tu(1:80,40)=tu(1:80,39)
tu(1:80,50)=tu(1:80,51)
tu(80,40:50)=tu(81,40:50)

if ((it/500)*500.eq.it) then
write(10, '(100f15.5)') tu
endif

tv=tu

enddo

write(20, '(100f15.5)') tu

stop
end