Simple data controlled loop: add numbers until you hit a 0

	program adder;
	var
		sum, n: integer;
	begin
	sum := 0;
        readln(n);
	while n <> 0 do
		begin
		sum := sum + n;
		writeln(sum);
		readln(n)
		end;
	end.

Sample output

<30
>30
<20
>50
<12
>62
<-5
>57
<100
>157
<0