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#include <bits/stdc++.h>
using namespace std;
#define rep(a, b) for (int a = 0; a < (b); a++)
#define rep1(a, b) for (int a = 1; a <= (b); a++)
#define all(x) (x).begin(), (x).end()
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int MOD = 1e9 + 7;

#define LOCAL false

const int LIM = 8007;
int n, k, t;

string str;
int pref[3][LIM];

int rcnt(int x, int l, int r) {
    return pref[x][r]-pref[x][l-1];
}

int get(int l, int r) {
    int wl = l+t;
    int wr = r-t;
    int rem = k-rcnt(1, l, wl-1)-rcnt(1, wr+1, r)-rcnt(0, 1, wl-1)-rcnt(0, wr+1, n);
    if (rem < 0) return -1;
    int work = rcnt(1, 1, l-1)+rcnt(1, r+1, n);
    int tot = n-(r-l+1);
    return tot-work+min(work, rem);
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    if (LOCAL) {
        ignore=freopen("io/in", "r", stdin);
        ignore=freopen("io/out", "w", stdout);
    }

    cin >> n >> k >> t;
    cin >> str;

    rep1(i, (int)str.size()) {
        rep(x, 3) pref[x][i] = pref[x][i-1];
        pref[str[i-1]-'1'][i]++;
    }

    int ans = -1;
    if (pref[0][n] <= k) ans = n-pref[1][n]+min(pref[1][n], k-pref[0][n]);
    rep1(i, n) for (int j = i+2*t-1; j <= n; j++) ans = max(ans, get(i, j));
    cout << ans << "\n";

    return 0;
}