#!/bin/python

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    cp = p
    cnt = 0
    while(s>=cp):
        cnt+=1
        s-=cp
        cp = max(cp-d,m)
    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