#include <bits/stdc++.h>
#ifdef SHARAELONG
#include "../../cpp-header/debug.hpp"
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;

void solve() {
    int n, k;
    cin >> n >> k;
    vector<int> a(n);
    for (int& x: a) cin >> x;
    string s;
    cin >> s;
    
    vector<int> pos;
    for (int i=0; i<n; ++i) {
        if (s[i] == '1') pos.push_back(i);
    }

    int ans = 0;
    multiset<int> ms[2];
    int l = 0, r = 0;
    for (int i=0; i+k<=pos.size(); ++i) {
        while (r <= pos[i+k-1]) {
            ms[s[r]-'0'].insert(a[r]);
            r++;
        }
        while (l < pos[i]) {
            auto it = ms[s[l]-'0'].find(a[l]);
            ms[s[l]-'0'].erase(it);
            l++;
        }

        assert(ms[1].size() == k);
        assert(ms[0].size() + ms[1].size() == r-l);
        int m = *ms[1].begin();
        if (ms[0].empty() || *prev(ms[0].end()) < m) ans = max(ans, m);
    }
    cout << ans;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    solve();
}