#!/bin/python3

import math
import os
import random
import re
import sys

#
# Complete the 'minimumPasses' function below.
#
# The function is expected to return a LONG_INTEGER.
# The function accepts following parameters:
#  1. LONG_INTEGER m
#  2. LONG_INTEGER w
#  3. LONG_INTEGER p
#  4. LONG_INTEGER n
#

def checkIfMidPassesPossible(m, w, p, n, rounds):
    candies = 0
    while rounds > 0:
        if m * w >= n:
            return True
        remaining_candies = n - candies
        needed_rounds = math.ceil(remaining_candies / (m * w))
        if needed_rounds <= rounds:
            return True
        if candies < p:
            rounds_needed_to_buy = math.ceil((p - candies) / (m * w))
            if rounds_needed_to_buy >= rounds:
                return False
            rounds -= rounds_needed_to_buy
            candies += rounds_needed_to_buy * m * w
        candies -= p
        if m <= w:
            m += 1
        else:
            w += 1
    return False

def minimumPasses(m, w, p, n):
    #Write your code here
    if p > n:
        return math.ceil(n / (m * w))
    low, high = 1, 10**12
    while low < high:
        mid = (low + high) // 2
        if checkIfMidPassesPossible(m, w, p, n, mid):
            high = mid
        else:
            low = mid + 1
    return low

if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')

    first_multiple_input = input().rstrip().split()

    m = int(first_multiple_input[0])

    w = int(first_multiple_input[1])

    p = int(first_multiple_input[2])

    n = int(first_multiple_input[3])

    result = minimumPasses(m, w, p, n)

    fptr.write(str(result) + '\n')

    fptr.close()