import sys
input = sys.stdin.readline

T = int(input())
N = int(input())
c = list(map(int, input().split()))
v = list(map(int, input().split()))
dp = [0] * (T+1)
for i in range(N):
    for j in range(T)[::-1]:
        k = 1
        x = v[i]
        s = x
        while j + k*c[i] <= T and x > 0:
            dp[j+k*c[i]] = max(dp[j+k*c[i]], dp[j] + s)
            x //= 2
            s += x
            k += 1
print(dp[T])