n, m, p, q = map(int, input().split())
leaf = 0
i = 1

while leaf < n:
    check = i % 12
    if p <= check <= p + q - 1:
        leaf += m * 2
    elif i % 12 == 0 and p + q - 1 == 12:
        leaf += m * 2
    else:
        leaf += m
    if leaf == n:
        break
    i += 1

print(i)