import math
import sys
# import os
# import numpy as np
# f = open('input.txt', 'r')
# sys.stdin = f

a, b, c, d = map(int, input().split())
sum_ = 0
yasai = 0
niku = 0
while sum_ <= d-c-1 and niku <= b-c and yasai <= a-1:
    niku += c
    yasai += 1
    sum_ = niku + yasai

print(yasai)