n,m,p,q = list(map(int,input().split()))
fin = 0
i = 1
while True :
    k = i % 12
    if k == 0 :
        k = 12
    if p <= k and k < p + q :
        n -= m *2
        if n <= 0 :
            fin = i
            break
    else :
        n -= m
        if n <= 0 :
            fin = i
            break
    i += 1

print(fin)