-- Homework 18, challenge: Sum 1..N.
--
-- Prompt for a positive whole number n. Compute 1 + 2 + ... + n with
-- a for loop and a running total. Print:
--   Sum from 1 to N is S
-- Then print the closed-form result n * (n + 1) / 2 on the next line
-- to confirm the two match.
--
-- Run with: lua exercises/18/homework/04-sum-1-to-n.lua

-- Your code goes here: