from itertools import cycle
from sys import stdin

def main():
    N, M, P, Q = map(int, input().split())

    cnt = 0
    for i in cycle(range(1, 13)):
        if P <= i < P + Q:
            N -= 2 * M
        else:
            N -= M
        cnt += 1
        if N <= 0:
            break
    print(cnt)

input = lambda: stdin.readline().rstrip()
main()