#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    cnt = 0
    curr = p
    while s >= curr:
        cnt += 1
        s -= curr
        curr = max(curr-d,m)
    return cnt
        

if __name__ == "__main__":
    p, d, m, s = input().strip().split(' ')
    p, d, m, s = [int(p), int(d), int(m), int(s)]
    answer = howManyGames(p, d, m, s)
    print(answer)