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#include <iostream>
#include <queue>
#include <vector>
#include <unordered_map>
#include <unordered_set>

using namespace std;

struct State {
    int time, skip, location, tasks;
    bool wasInOffice;

    State(int t, int s, int l, int ts, bool w) : time(t), skip(s), location(l), tasks(ts), wasInOffice(w) {}

    State() : time(0), skip(0), location(0), tasks(0), wasInOffice(false) {}

    bool operator==(const State &other) const {
        return time == other.time && skip == other.skip && location == other.location &&
               tasks == other.tasks && wasInOffice == other.wasInOffice;
    }

    bool operator!=(const State &other) const {
        return !(*this == other);
    }
};

struct StateHash {
    size_t operator()(const State &s) const {
        return hash<int>()(s.time) ^ hash<int>()(s.skip) ^ hash<int>()(s.location) ^
               hash<int>()(s.tasks) ^ hash<bool>()(s.wasInOffice);
    }
};

int countMissedMeetings(const string &s, int start, int duration) {
    int missed = 0;
    for (int i = start; i < min((int)s.size(), start + duration); i++) {
        if (s[i] == '1' || s[i] == '2') missed++;
    }
    return missed;
}

int main() {
    int n, k, t;
    cin >> n >> k >> t;
    string s;
    cin >> s;

    unordered_set<State, StateHash> visited;

    queue<State> q;
    State start(0, 0, 0, 0, false);
    int missed = countMissedMeetings(s, 0, t);
    State startInOffice(t, missed, 1, 0, true);
    q.push(start);
    q.push(startInOffice);
    visited.insert(start);
    visited.insert(startInOffice);

    State best_state(0, 0, 0, -1, false);

    while (!q.empty()) {
        State state = q.front();
        q.pop();

        int curr_time = state.time, curr_skip = state.skip;
        int curr_location = state.location, curr_tasks = state.tasks;
        bool curr_wasInOffice = state.wasInOffice;

        if (curr_time == n && curr_tasks > best_state.tasks && curr_skip <= k && curr_location == 0) {
            best_state = state;
        }
        if (curr_time == n) continue;

        char event = s[curr_time];

        if (curr_location == 0) {
            // Spotkanie online
            State next(curr_time + 1, curr_skip, 0, curr_tasks, curr_wasInOffice);
            if (event == '2' && visited.find(next) == visited.end()) {
                visited.insert(next);
                q.push(next);
            }
            // Zadanie
            next = State(curr_time + 1, curr_skip, 0, curr_tasks + 1, curr_wasInOffice);
            if (event == '3' && visited.find(next) == visited.end()) {
                visited.insert(next);
                q.push(next);
            }
            // Podroz
            int missed = countMissedMeetings(s, curr_time, t);
            if (curr_skip + missed <= k) {
                next = State(curr_time + t, curr_skip + missed, 1, curr_tasks, true);
                if (!curr_wasInOffice && visited.find(next) == visited.end()) {
                    visited.insert(next);
                    q.push(next);
                }
            }
            // Pominięcie
            next = State(curr_time + 1, curr_skip + 1, 0, curr_tasks + 1, curr_wasInOffice);
            if ((event == '1' || event == '2') && curr_skip < k && visited.find(next) == visited.end()) {
                visited.insert(next);
                q.push(next);
            }
        } else {
            // Spotkanie w biurze
            State next(curr_time + 1, curr_skip, 1, curr_tasks, curr_wasInOffice);
            if ((event == '1' || event == '2') && visited.find(next) == visited.end()) {
                visited.insert(next);
                q.push(next);
            }
            // Powrot do domu
            int missed = countMissedMeetings(s, curr_time, t);
            if (curr_skip + missed <= k) {
                next = State(curr_time + t, curr_skip + missed, 0, curr_tasks, curr_wasInOffice);
                if (visited.find(next) == visited.end() && curr_time + t <= n) {
                    visited.insert(next);
                    q.push(next);
                }
            }
            // Pominiecie zadania
            next = State(curr_time + 1, curr_skip, 1, curr_tasks, curr_wasInOffice);
            if (event == '3' && visited.find(next) == visited.end()) {
                visited.insert(next);
                q.push(next);
            }
        }
    }

    if (best_state.tasks == -1) {
        cout << -1 << endl;
    } else {
        cout << best_state.tasks << endl;
    }


    return 0;
}