#include <bits/stdc++.h>
using namespace std;
#define int long long

#define dbg(x...) \
do { \
std::cout << #x << " -> "; \
err(x); \
} while (0)

void err() {
	std::cout << std::endl;
}

template<class T, class... Ts>
void err(T arg, Ts &... args) {
	std::cout << fixed << setprecision(10) << arg << ' ';
	err(args...);
}

void GENSHEN_START() {
	int n,k;cin >> n >> k;
	vector<int>a(n + 5);
	for (int i = 0;i < n;i++) cin >> a[i];
	string res;cin >> res;
	int st = -1,ed = -1;
	int cnt = 0,mx = 0;
	for (int i = 0;i < n;i++) {
		if (res[i] == '1') cnt++,mx = max(mx,a[i]);
		if (cnt == 1 && st == -1) st = i;
		if (cnt == k) {
			ed = i;
			break;
		}
	}
	if (ed == -1) {
		cout << 0 << '\n';
		return ;
	}
	if (k == 1) {
		cout << mx << '\n';
		return ;
	}
	//dbg(st,ed);
	multiset<int>num0,num1;
	for (int i = st;i <= ed;i++) {
		if (res[i] == '0') num0.insert(a[i]);
		else num1.insert(a[i]);
	}
	int ans = 0;
	while (1) {
		int mi1 = *(num1.begin()),mx0 = 0;
		if (!num0.empty()) mx0 = *(num0.rbegin());
		if (mi1 > mx0) ans = max(ans,mi1);
		//dbg(ans,mi1,mx0);
		int ok1 = 0,ok2 = 0;
		for (int i = st;i <= n;i++) {
			if (i == st) num1.erase(num1.find(a[i]));
			else if (res[i] == '0') num0.erase(num0.find(a[i]));
			else {
				ok1 = 1;
				st = i;
				num1.insert(a[i]);
				break;
			}
		}
		for (int i = ed;i <= n;i++) {
			if (i == ed) num1.erase(num1.find(a[i]));
			else if (res[i] == '0') num0.insert(a[i]);
			else {
				ok2 = 1;
				ed = i;
				num1.insert(a[i]);
				break;
			}
		}
		if (ok1 == 0 || ok2 == 0) break;
	}
	cout << ans << '\n';
	return ;
}

signed main()
{
	ios::sync_with_stdio(false);cin.tie(nullptr);
	int T = 1;
	//cin >> T;
	while (T--) GENSHEN_START();
	return 0;
}