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#include <bits/stdc++.h>

using namespace std;

constexpr int nax = 8e3 + 1, inf = 1e4;

int dp[nax + 1][nax][3];
int pref[nax];

int range_sum(int l, int r) {
    return pref[r] - (l > 0 ? pref[l - 1] : 0);
}

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

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

    string s;
    cin >> s;
    s += '3';

    dp[0][0][0] = 0;
    dp[0][0][1] = -inf;
    dp[0][0][2] = 0;
    for (int i = 1; i <= k; ++i) {
        fill(dp[0][i], dp[0][i] + 3, -inf);
    }

    for (int i = 1; i <= n + 1; ++i) {
        for (int j = 0; j <= k; ++j) {
            fill(dp[i][j], dp[i][j] + 3, -inf);
            int m = range_sum(i - t, i - 1);

            dp[i][j][1] = dp[i - 1][j][1];
            if (i - t - 1 >= 0 and m <= j) {
                dp[i][j][1] = max(dp[i][j][1], dp[i - t - 1][j - m][0]);
            }

            if (s[i - 1] == '1') {
                if (j) {
                    dp[i][j][0] = dp[i - 1][j - 1][0] + 1;  
                    dp[i][j][2] = dp[i - 1][j - 1][2] + 1;
                }

                if (i - t - 1 >= 0 and m + 1 <= j) {
                    dp[i][j][2] = max(dp[i][j][2], dp[i - t - 1][j - m - 1][1]);
                }
            } else if (s[i - 1] == '2') {
                dp[i][j][0] = dp[i - 1][j][0];
                dp[i][j][2] = dp[i - 1][j][2];
                if (j) {
                    dp[i][j][0] = max(dp[i][j][0], dp[i - 1][j - 1][0] + 1);
                    dp[i][j][2] = max(dp[i][j][2], dp[i - 1][j - 1][2] + 1);
                }
                if (i - t - 1 >= 0 and m <= j) {
                    dp[i][j][2] = max(dp[i][j][2], dp[i - t - 1][j - m][1]);
                }
                if (i - t - 1 >= 0 and m + 1 <= j) {
                    dp[i][j][2] = max(dp[i][j][2], dp[i - t - 1][j - m][1]);
                }
            } else {
                dp[i][j][0] = dp[i - 1][j][0] + 1;
                dp[i][j][2] = dp[i - 1][j][2] + 1;

                if (i - t - 1 >= 0 and m <= j) {
                    dp[i][j][2] = max(dp[i][j][2], dp[i - t - 1][j - m][1] + 1);
                }
            }

            dp[i][j][2] = max(dp[i][j][2], dp[i][j][0]);
        }
        pref[i] = pref[i - 1] + (s[i - 1] == '1' or s[i - 1] == '2');
    }

    int res = -1;
    for (int i = 0; i <= k; ++i) {
        res = max(res, dp[n + 1][i][2] - 1);
    }

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