#!/bin/python3

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

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)