#!/bin/python3

import sys

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

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)