#!/bin/python

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    ret = []
    ss = 0
    while ss < s:
        
        if len(ret) == 0:
            ret.append(p)
            ss += p
        else:
            temp = 0
            if ret[-1]-d <=  m:
                temp = m
            else:
                temp = ret[-1] -d
            ret.append(temp)
            ss += temp
        #print ss,ret, ret[-1]
    temp = len(ret)
    if sum(ret) > s:
        temp -= 1
    return temp
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