import strutils, sequtils

var
  NMPQ = map(split(readLine(stdin)),parseInt)
  N = NMPQ[0]
  M = NMPQ[1]
  P = NMPQ[2]
  Q = NMPQ[3]
  count = 0

block loop :
  while N >= 0 :
    for i in countup(1,12) :
      count += 1
      
      if i >= P and i <= P+Q-1 :
        N -= M*2 
      else :
        N -= M
      
      if N <= 0 :
        break loop

echo count