#!/bin/python

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    n1 = 0
    n2 = 0
    s1 = 0
    while(p > m):
        s1 += p
        p -= d
        if(s1 <= s):
            n1 += 1
        else:
            break
    n2 = max((s - s1) / m, 0)
    return n1 + n2
    

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