#!/bin/python3

import sys

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)
rem= s-p
#print (rem)
answer=1
while rem >= 0:
    if (rem > m): 
        rem -= (p-d)
        if p>d:
            p=p-d
        else:
            break
        answer=answer+1
        #print (rem)
    else:
        while rem>=0:
            rem= rem-m
            if rem>=0:
                answer=answer+1
            #print (rem)
print (answer)