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#include <bits/stdc++.h>

using namespace std;

int solve()
{
    int n, t, k;
    char s[8008];
    scanf("%d%d%d%s", &n, &k, &t, s);
    vector<int> s_any(n + 1, 0);
    vector<int> s_remote(n + 1, 0);
    for (int i = 0; i < n; i++) {
        s_any[i + 1] = s_any[i] + (s[i] != '3');
        s_remote[i + 1] = s_remote[i] + (s[i] == '2');
    }
    int must_meet = max(s_any[n] - k, 0);
    if (s_any[n] - s_remote[n] <= k)
        return n - must_meet;
    int best = -1;
    auto check = [&](int i, int j) {
        int in_office = s_any[j - t] - s_any[i + t];
        int can_meet = s_remote[i] + s_remote[n] - s_remote[j] + in_office;
        if (can_meet >= must_meet)
            best = max(best, n - j + i + in_office - must_meet);
        return can_meet >= must_meet;
    };
    for (int i = 0; i <= n - 2 * t; i++) {
        int l = i + 2 * t, r = n + 1;
        while (l + 1 < r) {
            int j = (l + r) / 2;
            if (check(i, j))
                r = j;
            else
                l = j;
        }
    }
    return best;
}

int main()
{
    printf("%d\n", solve());
}