#!/bin/python

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    g = 0
    t = p
    to = p
    while s >= to:
        if t-d > m:
            t -= d
            to += t
            g += 1
        else:
            t = m
            to += t
            g += 1
    return g

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