#!/bin/python

import sys

def howManyGames(p, d, m, s):
    left,count,price = s,0,p
    while(True):
        if left == 0:
            break
        
        if price <= m:
            price = m
        
        left = left - price
        if left < 0:
            break
        else:
            count += 1
        
        newPrice = price - d
        if newPrice <= m:
            newPrice = m
        price = newPrice
    return count
        

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