-module(solution).
-export([main/0]).

main() ->
  {ok, [P, D, M, S]} = io:fread("", "~d~d~d~d"),
  N = games(P, D, M, S),
  io:format("~p~n", [N]),
  true.

games(P, D, M, S) ->
  games(P, D, M, S, 0).

games(P, _D, _M, S, N) when P > S ->
  N;
games(P, D, M, S, N) ->
  P2 = max(P-D, M),
  S2 = S-P,
  N2 = N+1,
  games(P2, D, M, S2, N2).