#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    x = p
    sum = 0
    c = 0
    while(sum + x <= s):
        sum += x
        x -= d
        x = max(x, m)
        c += 1
    return c
        

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)