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#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define pb push_back
#define st first
#define nd second
const int MAXN = 1e4 + 7;
int pref[MAXN][3];

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;
    rep(i, n) {
        rep(c, 3) {
            pref[i + 1][c] = pref[i][c];
        }
        int c = s[i] - '1';
        pref[i + 1][c]++;
    }
    int ans = -1;
    if (pref[n][0] <= k) {
        ans = max(ans, pref[n][0] + pref[n][2] + min(k - pref[n][0], pref[n][1]));
    }
    for (int i = t; i < n; i++) {
        for (int j = i; j < n - t; j++) {
            int ile = 0;
            ile += (pref[i][0] - pref[i - t][0]) + (pref[i][1] - pref[i - t][1]);
            ile += (pref[j + t + 1][0] - pref[j + 1][0]) + (pref[j + t + 1][1] - pref[j + 1][1]);
            // cout << "ile = " << ile << '\n';
            ile += pref[i - t][0];
            ile += pref[n][0] - pref[j + t + 1][0];
            int suma = pref[i - t][0] + pref[i - t][2] + (pref[n][0] + pref[n][2] - pref[j + t + 1][0] - pref[j + t + 1][2]);
            int pom = pref[i - t][1] + (pref[n][1] - pref[j + t + 1][1]);
            // cout << "i = " << i << " j = " << j << " suma = " << suma << " lef = " << k - ile << " pom = " << pom << '\n';
            if (ile <= k) {
                int lef = k - ile;
                ans = max(ans, suma + min(lef, pom));
            }
        }
    }
    cout << ans << '\n';
    return 0;
}