rec ack:=prog(a: array of int, b: array of int) of
array of int{
	if(len a==0){
		bb:array[len b+1] of int=mk();
		become bb;
	}
	if(len b==0){
		aa:array[len a-1] of int=mk();
		b:array[1] of int=mk();
		become ack(aa, b);
	}
	bb:array[len b-1] of int=mk();
	b=ack(a, bb);
	aa:array[len a-1] of int=mk();
	become ack(aa, b);
};
x:array[3] of int=mk();
y:array[4] of int=mk();
len ack(x, y);
