real tv(100,100),tu(100,100),alpha
	data tv,tu/20000*0./
	
	read *, nt
	open (10,file="s_2d_1.out")
	alpha=0.05
c******* alg tingimused *********************** 

	do i=1,100
	tv(i,1)=100.
	enddo

c**********************************************

	do k=1,nt
	 
	do i=2,99
	do j=2,99
	
	sum=alpha*(tv(i+1,j)-4.*tv(i,j)+tv(i-1,j)+tv(i,j+1)+tv(i,j-1))
        tu(i,j)=tv(i,j)+sum
	
	enddo
	enddo
	
c******  raja tingimused **********************

	do i=1,100
	tu(i,1)=100.
	enddo

	do i=2,100
	tu(1,i)=tu(2,i)
	tu(i,100)=tu(i,99)
	tu(100,i)=tu(99,i)
	enddo

c***********************************************
	do i=1,100
	do j=1,100
	tv(i,j)=tu(i,j)
	enddo
	enddo	
	
	if((k/1000)*1000.eq.k)then
	write(10,100) tu
100	format(100e15.5)
	endif

	enddo
	
	stop
	end