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#include <cstdio>

const int maxN = 8010;
char S[maxN];
int pref[4][maxN];

const int OFFICE = 1;
const int ONLINE = 2;
const int FREE = 3;
int N, K, T;

int max(int a, int b)
{
    return a > b ? a : b;
}

int min(int a, int b)
{
    return a < b ? a : b;
}

int count(int X, int a, int b)
{
    return pref[X][b + 1] - pref[X][a];
}

int main()
{
    scanf("%d%d%d", &N, &K, &T);
    scanf("%s", S);

    for (int i = 1; i <= N; ++i)
    {
        pref[FREE][i] = pref[FREE][i - 1] + (S[i - 1] == '0' + FREE);
        pref[ONLINE][i] = pref[ONLINE][i - 1] + (S[i - 1] == '0' + ONLINE);
        pref[OFFICE][i] = pref[OFFICE][i - 1] + (S[i - 1] == '0' + OFFICE);
    }

    if (count(OFFICE, 0, N - 1) <= K)
    {
        K -= count(OFFICE, 0, N - 1);
        printf("%d\n", min(N, N - count(ONLINE, 0, N - 1) + K));
        return 0;
    }

    int best = -1;
    for (int i = 0; i <= N - 2 * T; ++i)
        for (int j = i + T; j <= N - T; ++j)
        {
            int k = K - (count(OFFICE, 0, i + T - 1) + count(OFFICE, j, N - 1) + count(ONLINE, i, i + T - 1) + count(ONLINE, j, j + T - 1));
            if (k >= 0)
            {
                int res = count(FREE, 0, i - 1) + count(FREE, j + T, N - 1);
                res += min(k, count(ONLINE, 0, i - 1) + count(ONLINE, j + T, N - 1));
                best = max(best, res);
            }
        }

    printf("%d\n", best);
}