#!/bin/ruby

def howManyGames(p, d, m, s)
    # Return the number of games you can buy
  numOfGames = 0

    if s >= p
      numOfGames += 1
      s = s - p
      gamePrice = p - d
    else
      return 0
    end

    if s >= gamePrice
      while gamePrice > m && gamePrice < s
        s = s - gamePrice
        gamePrice = gamePrice - d
        numOfGames += 1
      end

      while s >= m
        s = s - m
        numOfGames += 1
      end
    end

    return numOfGames
end

p, d, m, s = gets.strip.split(' ')
p = p.to_i
d = d.to_i
m = m.to_i
s = s.to_i
answer = howManyGames(p, d, m, s)
puts answer