#include<bits/stdc++.h>

using i64 = long long;
using l64 = long double;

template<class T>
struct RMQ {
    int n;
    std::vector<T> a;
    std::vector<std::array<T, 30>> f;
    std::function<T(T, T)> func;

    RMQ() {};

    RMQ(std::vector<T> init_, std::function<T(T, T)> func_) {
        work(init_, func_);
    }

    void work(std::vector<T> &init_) {
        work(init_, [&](T x, T y) { return std::max(x, y); });
    }

    void work(std::vector<T> &init_, std::function<T(T, T)> func_) {
        this->a = init_;
        this->func = func_;
        this->n = a.size();
        this->f.assign(n, {});
        for (int i = 0; i < n; i++) f[i][0] = a[i];
        for (int j = 1; j <= std::__lg(n) + 1; j++) {
            for (int i = 0; i + (1 << j) - 1 < n; i++) {
                f[i][j] = func(f[i][j - 1], f[i + (1 << (j - 1))][j - 1]);
            }
        }
    }

    T query(int l, int r) {
        int k = std::__lg(r - l + 1);
        return func(f[l][k], f[r - (1 << k) + 1][k]);
    }
};

void DAOQI() {
    int n, k;
    std::cin >> n >> k;
    std::vector<int> rat(n + 1);
    for (int i = 1; i <= n; i++)std::cin >> rat[i];
    RMQ<int> rmq;
    rmq.work(rat, [&](int x, int y) {
        return std::min(x, y);
    });
    std::string s;
    std::cin >> s;
    s = " " + s;
    int ans = 0;
    for (int l = 1, r = 1; r <= n; r++) {
        if (s[r] == '0') {
            l = r + 1;
            continue;
        }
        if (r - l + 1 > k) l++;
        if (r - l + 1 == k) {
            ans = std::max(ans, rmq.query(l, r));
        }
    }
    std::cout << ans << "\n";
}

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