import Data.List
import qualified Data.Map as Map
import Text.Printf

f::Int->Int->Int->Int->Int->Int
f n m p q ans
    |n<=0=ans
    |(p <= ((ans `mod` 12)+1)) && (((ans `mod` 12)+1) <=q) =f (n-(2*m)) m p q (ans+1)
    |otherwise=f (n-m) m p q (ans+1)

main =do
      t<-getLine
      let (n:m:p:q:[])=map read (words t)::[Int]
          d=m*(12+q)
      print $ f (n `mod` d) m p (p+q-1) ((n `div` d)*12)