#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    count = 0
    
    cost = 0
    while s >= 0:    
        if (count == 0):
            cost = p
        else:
            cost = max(cost - d, m)
            
        s -= cost
        count += 1
    
    return count - 1

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)