#!/bin/python3

import sys

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

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)