n, m, p, q = list(map(int, input().split()))

l1 = []
for i in range(p, p+q):
    l1.append(i)

for j in range(100000):
    for i in range(1, 13):
        if i in l1:
            n -= m*2
        else:
            n -= m
        if n <= 0:
            print(12*j + i)
            break
    if n <= 0:
        break