#!/bin/python

import sys

def howManyGames2(p, d, m, s):
    count=0
    if s<p:
        return 0
    count+=1
    s=s-p
    n=(p-m)/d
    
    while s>value:
        count+=1
        s=s-value
        if (value-d) >m:
            value=value-d
        else:
            value=m
    return count
def howManyGames(p, d, m, s):
    count=0
    value=p
    while s>=value:
        count+=1
        s=s-value
        if (value-d) >m:
            value=value-d
        else:
            value=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