import sys


def main():
    N, M, P, Q = map(int, input().split())
    n = N
    m = 1

    for i in range(1, sys.maxsize):
        if P <= m < P + Q:
            n -= M

        n -= M

        m += 1
        if m > 12:
            m = 1

        if n <= 0:
            print(i)
            break


main()