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#include <vector>
#include <iostream>

using namespace std;

class Counter {
    string m_schedule;
    int m_n;
    std::vector<int> officeAfter, remoteAfter;

public:
    explicit Counter(const int n, string schedule)
        : m_schedule(std::move(schedule)),
          m_n(n),
          officeAfter(n), remoteAfter(n) {
        officeAfter[n - 1] = m_schedule[n - 1] == '1' ? 1 : 0;
        remoteAfter[n - 1] = m_schedule[n - 1] == '2' ? 1 : 0;
        for (int i = n - 2; i >= 0; i--) {
            const auto office_count = m_schedule[i] == '1' ? 1 : 0;
            const auto remote_count = m_schedule[i] == '2' ? 1 : 0;
            officeAfter[i] = officeAfter[i + 1] + office_count;
            remoteAfter[i] = remoteAfter[i + 1] + remote_count;
        }
    }

    [[nodiscard]] int countOffice(const int from, const int to) const {
        if (from > to) {
            return 0;
        }
        if (from == to) {
            return m_schedule[from] == '1' ? 1 : 0;
        }

        const auto afterTo = officeAfter[to];
        const auto afterFrom = officeAfter[from];
        return afterFrom - afterTo + (m_schedule[to] == '1' ? 1 : 0);
    }

    [[nodiscard]] int countRemote(const int from, const int to) const {
        if (from > to) {
            return 0;
        }
        if (from == to) {
            return m_schedule[from] == '2' ? 1 : 0;
        }

        const auto afterTo = remoteAfter[to];
        const auto afterFrom = remoteAfter[from];
        return afterFrom - afterTo + (m_schedule[to] == '2' ? 1 : 0);
    }
};

int main() {
    ios_base::sync_with_stdio(false);

    int n, k, t;
    cin >> n >> k >> t;

    string word;
    cin >> word;

    const Counter counter(n, word);

    const auto office_meetings_cnt = counter.countOffice(0, n - 1);
    const auto remote_meetings_cnt = counter.countRemote(0, n - 1);

    if (office_meetings_cnt <= k) {
        // can stay home
        const auto mandatory_meetings_cnt = max(0, office_meetings_cnt + remote_meetings_cnt - k);
        cout << (n - mandatory_meetings_cnt) << endl;
    } else {
        // must go work
        int result = -1;
        for (int start = 0; start <= n - 2 * t; start++) {
            for (int end = start + t; end <= n - t; end++) {
                const int office_meetings_when_going_work = counter.countOffice(start, start + t - 1);
                const int remote_meetings_when_going_work = counter.countRemote(start, start + t - 1);
                const int office_meetings_when_going_home = counter.countOffice(end, end + t - 1);
                const int remote_meetings_when_going_home = counter.countRemote(end, end + t - 1);
                const int meetings_when_commuting =
                        office_meetings_when_going_work + remote_meetings_when_going_work +
                        office_meetings_when_going_home + remote_meetings_when_going_home;

                if (meetings_when_commuting > k) {
                    continue;
                }

                const int can_skip_yet = k - meetings_when_commuting;
                const int office_meetings_before_work = counter.countOffice(0, start - 1);
                const int office_meetings_after_work = counter.countOffice(end + t, n - 1);
                const int office_meetings_when_home = office_meetings_before_work + office_meetings_after_work;

                const int remote_meetings_before_work = counter.countRemote(0, start - 1);
                const int remote_meetings_after_work = counter.countRemote(end + t, n - 1);
                const int remote_meetings_when_home = remote_meetings_before_work + remote_meetings_after_work;

                if (office_meetings_when_home <= can_skip_yet) {
                    const int mandatory_meetings_cnt = max(
                        0, office_meetings_when_home + remote_meetings_when_home - can_skip_yet);
                    const int time_outside_home = end + t - start;
                    int local_result = n - mandatory_meetings_cnt - time_outside_home;
                    result = max(result, local_result);
                }
            }
        }
        cout << result << endl;
    }

    return 0;
}