#!/bin/python

import sys

def howManyGames(p, d, m, s):
    count=0
    sum=0
    while sum<=s:
        sum+=p
        if p>=m:
            p=p-d
            if p<m:
                p=m
        count+=1
    return count-1

if __name__ == "__main__":
    p, d, m, s = raw_input().strip().split(' ')
    p, d, m, s = [int(p), int(d), int(m), int(s)]
    answer = howManyGames(p, d, m, s)
    print answer