import sequtils, strutils

let
  nmpq = stdin.readLine.split.map parseInt
  n = nmpq[0]  # 初期値
  m = nmpq[1]  # 減 / 月
  p = nmpq[2]  # m2倍
  q = nmpq[3]  # pの長さ(ヶ月)

var
  month = 1
  cnt = n
  double = 0
  ans = 1

while true:
  cnt.dec m
  if month == p:
    double = q
  if double > 0:
    cnt.dec m
    double.dec
  if cnt <= 0:
    break
  month.inc
  if month > 12:
    month = 1
  ans.inc

echo ans