import sys
from itertools import count


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    n, m, p, q = map(int, input().split())
    for d in count(0):
        if p - 1 <= d % 12 < p - 1 + q:
            n -= 2 * m
        else:
            n -= m
        if n <= 0:
            return d + 1


if __name__ == '__main__':
    ret = main()
    if ret is not None:
        print(ret)