#include <bits/stdc++.h>

using namespace std;

int a[8080];
int ps[4][8080];

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

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

    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= 3; j++) {
            ps[j][i] = ps[j][i - 1] + (s[i - 1] - '0' == j);
        }
    }

    if(ps[1][n] <= k) {
        k -= ps[1][n];
        cout << n - max(0, ps[2][n] - k) << "\n";
        return 0;
    }

    int res = -1;
    for(int i = 1; i <= n; i++) {
        for(int j = i + t; j + t <= n + 1; j++) {
            int tmp_k = k;
            
            int way_meetings = 0;
            for(int k = 1; k <= 2; k++) {
                way_meetings += (ps[k][i + t - 1] - ps[k][i - 1]) + (ps[k][j + t - 1] - ps[k][j - 1]);
            }
            int home_onsite_meetings = 0;
            home_onsite_meetings += (ps[1][i - 1] - ps[1][0]) + (ps[1][n] - ps[1][j + t - 1]);

            int c = home_onsite_meetings;
            tmp_k -= way_meetings;
            tmp_k -= home_onsite_meetings;
            if(tmp_k < 0) {
                continue;
            }

            c += (ps[3][i - 1] - ps[3][0]) + (ps[3][n] - ps[3][j + t - 1]);

            res = max(res, c);
        }
    }

    cout << res << "\n";
    return 0;
}