#!/bin/python3

import sys

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

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)