1def ack(m, n)
2    if m == 0 then
3        n + 1
4    elsif n == 0 then
5        ack(m - 1, 1)
6    else
7        ack(m - 1, ack(m, n - 1))
8    end
9end
10
11NUM = 9
12ack(3, NUM)
13