#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    games = 0
    while s >= 0:
        if games == 0:
            cost = p
        elif cost == m:
            pass
        else:
            cost = cost - d
            if cost <= m:
                cost = m
        s -= cost
        games += 1
    return games - 1
    
    
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)