/*
	no limit 
	** KE4 **
*/

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

#define N 100010
#define ll long long
#define M 32

int a[N];

#define bit(x) (1 << (x))

struct RMQ {
    int n, v[M][N];

    void build (int *a, int sz) {
        int m; n = sz;
        for (int i = 0; i < n; i++) v[0][i] = a[i];
        for (int k = 0; (m = n - bit(k + 1)) >= 0; k++)
            for (int i = 0; i <= m; i++)
                v[k + 1][i] = min(v[k][i], v[k][i + bit(k)]);
    }

    int query (int st, int en) {
        if (st == en) return v[0][st];
        int k = 31 - __builtin_clz(en - st);
        return min(v[k][st], v[k][en - bit(k) + 1]);
    }
} R;

int main(){
	
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	int n, k;
	cin >> n >> k;
	for(int i = 0;i < n;i ++) cin >> a[i];
	string s;
	cin >> s;
	R.build(a, n);
	int cnt = 0, mn = 1e9, ans = 0;
	for(int i = 0;i < n;i ++) {
		if(s[i] == '1') cnt ++, mn = min(mn, a[i]);
		else {
			cnt = 0;
			mn = 1e9;
			continue;
		}
		if(cnt >= k) {
			int y = R.query(i - k + 1, i);
			ans = max(ans, mn);
			cnt --;
		}
	}
	cout << ans << endl;
	
	return 0;
}