#include <iostream>
using namespace std;
int a[10005], b[105], f[10005];

int main() {
	//freopen("game.in", "r", stdin);
	//freopen("game.out", "w", stdout);
	int n, m;
	cin >> n >> m;
	for (int i = 0; i < m; i++) {
		cin >> b[i];
	}
	for (int i = 0; i < n; i++) {
		cin >> a[i];
		f[i] = -2e9;
	}
	for (int i = n - 1; i >= 0; i--) {
		for (int j = 0; j < m; j++) {
			int t = f[b[j] + i];
			if (t > f[i]) {
				f[i] = t;
			}
		}
		f[i] += a[i];
	}
	cout << f[0];
	return 0;
}