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#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) {}
#endif

#define x first
#define y second
#define ir(a, x, b) ((a) <= (x) && (x) <= (b))
#define vec vector
#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define all(x) (x).begin(), (x).end()

using ll = long long;

int main() {
    cin.tie(0)->sync_with_stdio(0);
    int N, K, t;
    cin >> N >> K >> t;
    vec<int> pw(N+1), pr(N+1);
    string s; cin >> s;
    rep (n, 0, N) {
        pw[n+1] = pw[n];
        pr[n+1] = pr[n];
        if (s[n] == '1') pw[n+1]++;
        if (s[n] == '2') pr[n+1]++;
    }
    int best = -1;
    int min = max(0, pw[N] + pr[N] - K);
    debug(min);
    if (pr[N] >= min) {
        best = max(best, N - min);
    }
    rep (j, 0, N+1) rep (i, 0, j) {
        // at work [i, j)
        // can drive there
        if (i - t < 0) continue;
        if (j + t > N) continue;
        debug(i, j);
        int atwork = pw[j] - pw[i] + pr[j] - pr[i];
        int athome = pr[i-t] + (pr[N] - pr[j+t]);
        debug(atwork, athome);
        if (atwork + athome < min) continue;
        int doathome = min - atwork;
        best = max(best, N - (j - i + 2*t) - doathome);
    }
    cout << best << "\n";
    return 0;
}