#!/bin/python3

import sys

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

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)