C++ :

#include <bits/stdc++.h>
using namespace std;
#define int long long 
void read(int &p)
{
    p = 0;
    int k = 1;
    char c = getchar();
    while(c < '0' || c > '9')
    {
        if(c == '-')
        {
            k = -1;
        }
        c = getchar();
    }
    while(c >= '0' && c <= '9')
    {
        p = p * 10 + c - '0';
        c = getchar();
    }
    p *= k;
    return ;
}
void write_(int x)
{
    if(x < 0)
    {
        putchar('-');
        x = -x;
    }
    if(x > 9)
    {
        write_(x / 10);
    }
    putchar(x % 10 + '0');
}
void writesp(int x)
{
    write_(x);
    putchar(' ');
}
void writeln(int x)
{
    write_(x);
    puts("");
}
int n,m,a[1111],b[55555];
int dp[51111];
signed main()
{
    read(n),read(m);
    for(int i = 1;i <= m;i++)
    {
        read(a[i]);
    }
    for(int i = 0; i < n;i++)
    {
        read(b[i]);
    }
    memset(dp,0xcf,sizeof(dp));
    dp[0] = b[0];
    for(int i = 0;i < n;i++)
    {
        for(int j = 1;j <= m;j++)
        {
            dp[min(n,i + a[j])] = max(dp[min(n,i + a[j])],dp[i] + b[min(n,i + a[j])]);
        }
    }
    writeln(dp[n]);
    return 0;
}