#include <bits/stdc++.h>
#define DEBUG 1
using namespace std;

// Defines
#define fs first
#define sn second
#define pb push_back
#define eb emplace_back
#define mpr make_pair
#define mtp make_tuple
#define all(x) (x).begin(), (x).end()
// Basic type definitions
#if __cplusplus == 201703L // CPP17 only things
template <typename T> using opt_ref = optional<reference_wrapper<T>>; // for some templates
#endif
using ll = long long; using ull = unsigned long long; using ld = long double;
using pii = pair<int, int>; using pll = pair<long long, long long>;
#undef __GNUG__
#ifdef __GNUG__
// PBDS order statistic tree
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template <typename T, class comp = less<T>> using os_tree = tree<T, null_type, comp, rb_tree_tag, tree_order_statistics_node_update>;
template <typename K, typename V, class comp = less<K>> using treemap = tree<K, V, comp, rb_tree_tag, tree_order_statistics_node_update>;
// HashSet
#include <ext/pb_ds/assoc_container.hpp>
template <typename T, class Hash> using hashset = gp_hash_table<T, null_type, Hash>;
template <typename K, typename V, class Hash> using hashmap = gp_hash_table<K, V, Hash>;
const ll RANDOM = chrono::high_resolution_clock::now().time_since_epoch().count();
struct chash { ll operator()(ll x) const { return x ^ RANDOM; } };
#endif
// More utilities
int SZ(string &v) { return v.length(); }
template <typename C> int SZ(C &v) { return v.size(); }
template <typename C> void UNIQUE(vector<C> &v) { sort(v.begin(), v.end()); v.resize(unique(v.begin(), v.end()) - v.begin()); }
template <typename T, typename U> void maxa(T &a, U b) { a = max(a, b); }
template <typename T, typename U> void mina(T &a, U b) { a = min(a, b); }
const ll INF = 0x3f3f3f3f, LLINF = 0x3f3f3f3f3f3f3f3f;

const int MN = 1e5 + 1;
int N, K,
    R[MN];
string W;

multiset<int, greater<int>> sizes;
void addSize(int x) {
    sizes.insert(x);
}
void removeSize(int x) {
    sizes.erase(sizes.find(x));
}
int getMaxSize() {
    return *sizes.begin();
}

int dsu[MN], cnt[MN];
int rt(int x) { return x == dsu[x] ? x : dsu[x] = rt(dsu[x]); }
void merge(int x, int y) { // y -> x
    x = rt(x);
    y = rt(y);
    if (x == y) return;

    removeSize(cnt[x]);
    removeSize(cnt[y]);
    dsu[y] = x;
    cnt[x] += cnt[y];
    addSize(cnt[x]);
}
void dec(int x) {
    x = rt(x);
    removeSize(cnt[x]);
    cnt[x]--;
    addSize(cnt[x]);
}
int getCnt(int x) {
    return cnt[rt(x)];
}


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

    cin >> N >> K;
    for (int i = 0; i < N; i++)
        cin >> R[i];
    cin >> W;

    // init dsu
    for (int i = 0; i < N; i++) {
        dsu[i] = i;
        cnt[i] = W[i] == '1';
        addSize(cnt[i]);
    }

    // connect wins together first
    for (int i = 0; i < N - 1; i++) {
        if (W[i] == '1' && W[i + 1] == '1') {
            merge(i, i + 1);
        }
    }

    // group by rating
    map<int, vector<int>> idxMap;
    for (int i = 0; i < N; i++)
        idxMap[R[i]].pb(i);

    int bestRating = 0;
    // for (int i = 0; i < N; i++) {
    //     maxa(maxRun, getCnt(i));
    // }
    for (auto [r, idxs] : idxMap) {
        // printf("r=%d getMaxSize=%d\n", r, getMaxSize());
        // printf("idxs=[");
        // for (int i : idxs) printf("%d, ", i);
        // printf("]\n");

        if (getMaxSize() >= K) {
            bestRating = r;
        }

        // now remove the idxs
        for (int idx : idxs) {
            if (W[idx]) {
                dec(idx);
            }
            else {
                if (idx > 0)
                    merge(idx - 1, idx);
                if (idx < N - 1)
                    merge(idx, idx + 1);
            }
        }
    }

    cout << bestRating << '\n';

    return 0;
}