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

const int N = 8005;
const int K = 8005;
int dp[N][K][2];
int pref[N];

void count_pref(int n, string seg) {
    for (int i = 1; i <= n; i++) {
        pref[i] = pref[i - 1];
        if (seg[i - 1] != '3') pref[i]++;
    }
    return;
}

void prepare(int n, int k) {
    for (int j = 0; j <= n; j++) {
        for (int i = 0; i <= k; i++) {
            dp[j][i][0] = dp[j][i][1] = -1;
        }
    }
    dp[0][0][0] = 0;
    dp[0][0][1] = -1;
    return;
}

void solve(int n, int k, int t, string seg) {
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j <= k; j++) {
            bool house = (seg[i - 1] != '1');

            if (house) dp[i][j][0] = dp[i - 1][j][0];
            dp[i][j][1] = dp[i - 1][j][1];

            if (i - t - 1 >= 0 && j - (pref[i - 1] - pref[i - t - 1]) >= 0) {
                dp[i][j][1] = max(dp[i][j][1], dp[i - t - 1][j - (pref[i - 1] - pref[i - t - 1])][0]);
            }

            if (house) {
                int x = (seg[i - 1] == '3') ? 1 : 0;
                dp[i][j][0] = max(dp[i][j][0], dp[i - 1][j][0] + x);

                if (i - t - 1 >= 0 && j - (pref[i - 1] - pref[i - t - 1]) >= 0) {
                    dp[i][j][0] = max(dp[i][j][0], dp[i - t - 1][j - (pref[i - 1] - pref[i - t - 1])][1] + x);
                }

                if (seg[i - 1] == '2' && j > 0) {
                    dp[i][j][0] = max(dp[i][j][0], dp[i - 1][j - 1][0] + 1);
                    if (i - t - 1 >= 0 && j - (pref[i - 1] - pref[i - t - 1]) - 1 >= 0) {
                        dp[i][j][0] = max(dp[i][j][0], dp[i - t - 1][j - (pref[i - 1] - pref[i - t - 1]) - 1][1] + 1);
                    }
                }
            } else {
                if (j > 0) {
                    dp[i][j][0] = max(dp[i][j][0], dp[i - 1][j - 1][0] + 1);
                    if (i - t - 1 >= 0 && j - (pref[i - 1] - pref[i - t - 1]) - 1 >= 0) {
                        dp[i][j][0] = max(dp[i][j][0], dp[i - t - 1][j - (pref[i - 1] - pref[i - t - 1] - 1)][1] + 1);
                    }
                }
            }
        }
    }
    return;
}

void ans(int n, int k) {
    int res = -1;
    for (int i = 0; i <= k; i++) {
        res = max(res, dp[n][i][0]);
    }
    cout << res << endl;
    return;
}

int main() {
    cin.tie(0) -> sync_with_stdio(false);
    

    int n, k, t;
    string s;

    cin >> n >> k >> t;
    cin >> s;

    count_pref(n, s);
    prepare(n, k);
    solve(n, k, t, s);
    ans(n, k);

    return 0;
}