#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    sum=p
    count=0
    while p-d>m and sum<=s:
        sum = sum+ p-d
        p=p-d
        count=count+1
    while sum<=s:
        sum= sum+m
        count+=1
    return count
if __name__ == "__main__":
    p, d, m, s = input().strip().split(' ')
    p, d, m, s = [int(p), int(d), int(m), int(s)]
    answer = howManyGames(p, d, m, s)
    print(answer)