#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    ca = 0
    count = 0
    rate = p
    while(True):
        count = count + rate
        rate = rate - d
        if rate <= m:
            rate = m
            
        ca = ca + 1
        if(count>s):
            return ca-1
        elif(count==s):
            return ca
        
        
    
    

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)