Erlang Chocolates By Numbers
-module(chocolates_by_numbers).
-export([chocolates_by_numbers/2]).

chocolates_by_numbers(N, M) ->
    G = gcd(N, M),
    (N * M) div G div M.

gcd(N, M) when N rem M =:= 0 -> M;
gcd(N, M) -> gcd(M, N rem M).

This uses the greatest common divisor to figure out how many chocolates get eaten before the pattern repeats.