#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    if(p>s):
        return 0
    count=0
    sum=0
    while(p>m):
        k=sum
        sum=sum+p
        p=p-d
        count=count+1
        if(sum>s):
            return count-1
    count=count+(s-sum)//m
    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)