#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <limits.h>
#include <map>
#include <queue>
#include <set>
#include <string.h>
#include <vector>

using namespace std;
typedef long long ll;

int main() {
  int T;
  cin >> T;
  int N;
  cin >> N;

  int c;
  int C[N];
  memset(C, 0, sizeof(C));
  for (int i = 0; i < N; ++i) {
    cin >> C[i];
  }

  int v;
  int V[N][100];
  memset(V, 0, sizeof(V));
  for (int i = 0; i < N; ++i) {
    cin >> v;

    int k = 0;
    while (v > 0) {
      V[i][k] = v;
      v /= 2;
      ++k;
    }
  }

  int dp[T + 1];
  memset(dp, -1, sizeof(dp));
  dp[0] = 0;
  int ans = 0;

  for (int i = 0; i < N; ++i) {
    for (int t = T - 1; t >= 0; --t) {
      if (dp[t] < 0) continue;
      int k = 0;
      int tv = 0;

      while (V[i][k] > 0) {
        tv += V[i][k];
        int nt = t + C[i] * (k + 1);
        if (T < nt) break;

        int nv = dp[t] + tv;
        dp[nt] = max(dp[nt], nv);
        ans = max(ans, dp[nt]);
        ++k;
      }
    }
  }

  cout << ans << endl;

  return 0;
}