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

#define N 100050

int n, k, r[N];
int st, en, mid;

bool vis[N];
string str;

bool get(){
	for(int i = 1; i <= n; i ++)
		if(r[i] >= mid) vis[i] = 1;
		else vis[i] = 0;
	int x = 0;
	for(int i = 1; i <= n; i ++){
		if(vis[i] == 0 || str[i - 1] == '0'){
			x = 0;
			continue;
		}
		x ++;
		if(x == k) return 1;
	}
	return 0;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
	
	cin >> n >> k;
    for(int i = 1; i <= n; i ++)
    	cin >> r[i];
	cin >> str;
	en = N;
	while(en - st > 1){
		mid = (st + en) / 2;
		if(get()) st = mid;
		else en = mid;
	}
	cout << st << '\n';
    return 0;
}