use sys: call

function ack(m, n)
   if m<4
      if m<2
         return m+n+1
      elif m==2
         return 2*n+3
      else m==3
         return 2^(n+3)-3
      end
   elif n==0
      return ack(m-1, 1)
   else
      return ack(m-1, ack(m, n-1))
   end
end

function main
   print(ack(4,3))
end

call(10^6,main)