#!/bin/python

import sys

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

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