#!/bin/python

import sys

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

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