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

const int N = 8e3 + 5;

int Pref[2][N];

int Check(int n, int k)
{
    int missed = Pref[0][n];
    int taken = Pref[1][n];
    int left = k - missed;
    taken = max(0, taken - left);

    if(left < 0)
        return -1;
    return n - taken;
}

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

    int n, k, t;
    string A;
    cin >> n >> k >> t;
    cin >> A;
    A = "#" + A;

    for(int i = 1; i <= n; i++) {
        Pref[0][i] = Pref[0][i-1] + (A[i] == '1');
        Pref[1][i] = Pref[1][i-1] + (A[i] == '2');
    }
    
    int sol = Check(n, k);
    for(int i = t+1; i <= n; i++) {
        for(int j = i; j <= n-t; j++) {
            int missed = Pref[0][i-1] + (Pref[0][n] - Pref[0][j]);
            missed += (Pref[1][i-1] - Pref[1][i-t-1]) + (Pref[1][j+t] - Pref[1][j]);

            int taken = Pref[1][i-t-1] + (Pref[1][n] - Pref[1][j+t]);
            int left = k - missed;
            taken = max(0, taken - left);

            if(left < 0)
                continue;
            sol = max(sol, (n - (j+t) + (i-t-1)) - taken);
        }
    }
    cout << sol << "\n";
    return 0;
}