#!/bin/python

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    s1=s
    s1=s1-p
    n=1
    while(s1>m):
        n+=1
        #print s1
        s1=s1-(p-d)
    return n+1
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