import sys

sys.setrecursionlimit(10 ** 6)
import numpy as np

def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))

def main():
    t=II()
    n=II()
    cc=LI()
    vv=LI()
    dp=np.zeros(t+1,dtype="i8")
    for c,v in zip(cc,vv):
        while v:
            np.maximum(dp[t:c-1:-1],dp[t-c::-1]+v,out=dp[t:c-1:-1])
#            for i in range(t,c-1,-1):
#                dp[i]=max(dp[i],dp[i-c]+v)
            v>>=1
    print(dp[t])

main()