#!/bin/python3

import sys

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

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)