#!/bin/python

import sys

def howManyGames(p, d, m, s):
    cnt=0
    cst=p
    while s>=m:
        if (cst)<=m:
            cnt+=s/m
            s=0
        elif ((cst)>=0) and (s-cst>=0):
            cnt+=1
            s-=cst
            cst-=d
        else:
            s=0
    return cnt

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