#!/bin/python3

import sys

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

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)