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#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <string>
#include <climits>

using namespace std;

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

    int n, k, t;
    string activities;

    cin >> n >> k >> t >> activities;

    vector<vector<int>> cnt(3, vector<int>(n + 1));
    for (int i = 0; i < n; ++i) ++cnt[activities[i] - '1'][i + 1];
    for (int i = 0; i < 3; ++i) partial_sum(cnt[i].begin(), cnt[i].end(), cnt[i].begin());

    int res = INT_MIN;

    for (int b = 1; b <= n; ++b)
    {
        for (int e = b + t; e + t <= n + 1; ++e)
        {
            int missed_travel = cnt[0][b + t - 1] - cnt[0][b - 1];
            missed_travel += cnt[1][b + t - 1] - cnt[1][b - 1];
            missed_travel += cnt[0][e + t - 1] - cnt[0][e - 1];
            missed_travel += cnt[1][e + t - 1] - cnt[1][e - 1];

            int missed_home = cnt[0][b - 1] + cnt[0][n] - cnt[0][e + t - 1];
            int remote_home = cnt[1][b - 1] + cnt[1][n] - cnt[1][e + t - 1];
            int free_time = cnt[2][b - 1] + cnt[2][n] - cnt[2][e + t - 1];

            if (missed_travel + missed_home > k) continue;
            res = max(res, free_time + missed_home + min(remote_home, k - missed_travel - missed_home));
        }
    }

    if (cnt[0][n] <= k) res = max(res, cnt[2][n] + cnt[0][n] + min(cnt[1][n], k - cnt[0][n]));

    if (res < 0) cout << "-1";
    else cout << res;
}