#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

#define int long long

signed main() {
    int n, m;
    cin >> n >> m;
    vector<int> day(n), k(m + 2);
    for (int i = 0; i < n; ++i) {
        cin >> day[i];
        day[i]--;
    }
    for (int i = 1; i <= m; ++i) {
        cin >> k[i];
    }
    int l = -1, r = n;
    while (r - l > 1) {
        vector<pair<int, int>> loc;
        vector<bool> used(m, 0);
        int mid = (r + l) / 2;
        for (int i = mid; i >= 0; --i) {
            if (data[i] != -1 && !used[day[i]]) {
                used[day[i]] = true;
                loc.emplace_back(day[i], i);
            }
        }
        reverse(loc.begin(), loc.end());
        if (loc.size() < m) {
            l = mid;
        }
        int busy = 0;
        bool good = true;
        for (int i = 0; i < loc.size(); ++i) {
            int have = loc[i].second - busy;
            if (have >= k[loc[i].first]) {
                busy += k[loc[i].first] + 1;
            } else {
                good = false;
                break;
            }
        }
        if (!good) {
            l = mid;
        } else {
            r = mid;
        }
    }
    if (r == n) {
        cout << -1;
        return 0;
    }
    cout << r + 1;
    return 0;
}