#!/bin/python3
from itertools import count
def howManyGames(p, d, m, s):
    t = 0
    for i in count(0):
        t += p
        if t > s:
            return i
        p = max(p-d, m)

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)