#include "bits/stdc++.h"
using namespace std;

const int maxN = 2e5 + 10;
int pos[maxN];
bool bad[maxN];

bool find_subsequence (string &s,string &t) {
	int j = 0;
	for (int i = 0; i < (int) s.size(); ++i) {
		if (s[i] == t[j]) ++j;
		if (j == (int) t.size()) return true;
	}
	return false;
}

bool yes (string & s,string & t,int x) {
	for (int i = 1; i < maxN; ++i) bad[i] = false;
	for (int i = 1; i <= x; ++i) bad[pos[i]] = true;
	string s2 = "";
	for (int i = 0; i < (int) s.size(); ++i) {
		if (bad[i + 1] == true) continue;
		s2.push_back(s[i]);
	}
	if (find_subsequence(s2,t)) return true;
	else return false;
}

int main () {
	 ios::sync_with_stdio(false);
	 cin.tie(nullptr);
	 cout.tie(nullptr);
	 int T = 1;
	 //~ cin >> T;
	 for (int test_case = 1; test_case <= T; ++test_case) {
		string s,t;
		cin >> s >> t;
		int n = (int) s.size();
		for (int i = 1; i <= n; ++i) cin >> pos[i];
		int res = 0;
		int l = 1,r = n;
		while (l <= r) {
			long long mid = l + (r - l) / 2;
			if (yes(s,t,mid)) {
				l = mid + 1;
				res = mid;
			} else {
				r = mid - 1;
			}
		}
		cout << res << '\n';
	 }
	 //~ cerr << "Time elapsed :" << clock() * 1000.0 / CLOCKS_PER_SEC << " ms" << '\n';
}


Problem Link : https://codeforces.com/problemset/problem/778/A