#include "bits/stdc++.h"
#define rep(i, a, n) for (auto i = a; i <= (n); ++i)
#define revrep(i, a, n) for (auto i = n; i >= (a); --i)
#define all(a) a.begin(), a.end()
#define sz(a) (int)(a).size()
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } else return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } else return 0; }

int main() {
	ios::sync_with_stdio(0); cin.tie(0);

	int n, m; cin >> n >> m;
	vi as(n), bs(m);
	for (auto &x: as) cin >> x;
	for (auto &x: bs) {
		cin >> x;
		x--;
	}
	int sum = accumulate(all(as), 0);
	int ans = n + m;
	if (sum == 0) chmin(ans, 0);
	rep(i, 0, m - 1) {
		int x = bs[i];
		sum -= as[x];
		as[x] ^= 1;
		sum += as[x];
		if (sum <= i + 1) chmin(ans, i + 1);
	}
	chmin(ans, max(sum, m));
	printf("%d\n", ans);
	return 0;
}