N, M, P, Q = map(int, input().split())
res = 0
while True:
    for i in range(1, 13):
        res += 1
        if P <= i < P + Q:
            N -= 2 * M
        else:
            N -= M
        if N <= 0:
            print(res)
            break
    else:
        continue
    break