#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    cusum = 0
    cout = 0
    nxt = p
    while(cusum+nxt<=s):
    	cusum += nxt
    	# print(cusum)
    	if(nxt-d<= m):
    		nxt = m
    	else:
    		nxt -= d
    	cout += 1
    return cout


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)