#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    count = 0
    # Return the number of games you can buy
    if s >= p: 
        s -= p
        count += 1
    while p-(d*(count-1)) >= m:
        s -= p-(d*(count-1))
        count += 1
    if s >= m:
        count += (s/m).floor()
    return count

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)