#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

#define ff first
#define ss second
#define y1 y111
#define X first
#define Y second
#define mk make_pair
#define inb push_back
#define all(v) v.begin(), v.end()

const int MAXN = (int)1e6 + 9, MAXN1 = (int)2e4 + 7;
const int INFint = (int)1e9 + 7, P = 31;
const ll INFll = (ll)1e18 + 7, MOD = (ll)1e9 + 7;
const double INFfl = 1e18 * 4 + 7;
const double EPS = 1e-7;
const double PI = atan2(0, -1);

int solve();

int main()
{
#define TASK ""
#ifdef _DEBUG
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
#else
    //freopen(TASK".in", "r", stdin), freopen(TASK".out", "w", stdout);
#endif
    solve();
}

const int STRBUF = (int)1e6 + 7;
char buf[STRBUF];
string get_str()
{
    scanf(" %s", buf);
    return string(buf);
}

int solve()
{
    int n, m;
    scanf("%d %d", &n, &m);
    vi d(n), a(n);
    for (int i = 0; i < n; ++i)
        scanf("%d", &d[i]), --d[i];
    for (int i = 0; i < m; ++i)
        scanf("%d", &a[i]);
    int l = -1, r = n;
    auto check = [&](int x)
    {
        vector<pii> lst(m, mk(-1, 0));
        for (int i = 0; i < m; ++i)
            lst[i].Y = i;
        for (int i = 0; i < x; ++i)
        {
            if (d[i] != -1)
                lst[d[i]].X = i;
        }
        sort(all(lst));
        if (lst[0].X == -1)
            return 0;
        int bds = 0;
        for (int i = 0; i < m; ++i)
        {
            int id = lst[i].Y;
            if (bds + a[id] <= lst[i].X)
                bds += a[id] + 1;
            else
                return 0;
        }
        return 1;
    };
    while (r - l > 1)
    {
        int mid = l + r >> 1;
        if (check(mid))
            r = mid;
        else
            l = mid;
    }
    if (!check(r))
        puts("-1"), exit(0);
    printf("%d\n", r);
    return 0;
}