#include<bits/stdc++.h>

using namespace std;

const int N = 1e5 + 5;

int n,m,d[N],a[N];

bool flag[N];

bool check(int x)

{

    memset(flag,0,sizeof(flag));

    int cur = x - 1;//cur为当前剩余复习天数

    for(int i = x; i >= 1; i--)

    {

        cur = min(cur, i - 1);//最多也只能是i - 1天的复习时间

        if(d[i] && !flag[d[i]] && a[d[i]] <= cur)

        {

            flag[d[i]] = 1;

            cur -= a[d[i]] + 1;//+1为下次考试所占的一天

        }

    }

    for(int i = 1; i <= m; i++)

    {

        if(!flag[i])

            return 0;

    }

    return 1;

}

int main()

{

    int ans = -1;

    scanf("%d %d",&n,&m);

    for(int i = 1; i <= n; i++)

        scanf("%d",d+i);

    for(int i = 1; i <= m; i++)

        scanf("%d",a+i);

    int l = 1, r = n, mid;

    while(l <= r)

    {

        mid = (l + r) >> 1;

        if(check(mid))

            r = mid - 1, ans = mid;

        else

            l = mid + 1;

    }

    printf("%d\n",ans);

}