def solve():
    N, M, P, Q = map(int, input().split())
    ans = N // ((12 + Q) * M) * 12
    N %= (12 + Q) * M
    for i in range(1, 13):
        if P <= i <= P + Q - 1:
            N -= M * 2
        else:
            N -= M
        ans += 1
        if N <= 0:
            break
    return ans
print(solve())