m,n,p,q = map(int, input().split())
cnt = 0
while m > 0:
    for month in range(12):
        cnt += 1

        m -= n
        if(month+1 >= p and month+1 <= p+q-1):
            m -= n
        #print(m)
        if m <= 0:
            print(cnt)
            break