#!/bin/python

import sys

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

if __name__ == "__main__":
    p, d, m, s = raw_input().strip().split(' ')
    p, d, m, s = [int(p), int(d), int(m), int(s)]
    answer = howManyGames(p, d, m, s)
    print answer