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#include <bits/stdc++.h>
using namespace std;

int pref1[8007];
int pref2[8007];
int pref3[8007];

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int n, k, t;
    cin >> n >> k >> t;
    string s;
    cin >> s;
    for (int i = 1; i <= n; i++)
    {
        pref1[i] = pref1[i - 1];
        pref2[i] = pref2[i - 1];
        pref3[i] = pref3[i - 1];
        if (s[i - 1] == '1')
        {
            pref1[i]++;
        }
        if (s[i - 1] == '2')
        {
            pref2[i]++;
        }
        if (s[i - 1] == '3')
        {
            pref3[i]++;
        }
    }
    int odp = -1;
    if (k >= pref1[n])
    {
        odp = pref3[n] + pref1[n] + min(pref2[n], k - pref1[n]);
    }
    for (int startp = 0; startp <= n - 2 * t; startp++)
    {
        for (int koniecb = startp + 2 * t - 1; koniecb < n; koniecb++)
        {
            if (k - (pref1[startp + t] - pref1[startp]) - (pref2[startp + t] - pref2[startp]) - (pref1[koniecb + 1] - pref1[koniecb - t + 1]) - (pref2[koniecb + 1] - pref2[koniecb - t + 1]) >= pref1[startp] + (pref1[n] - pref1[koniecb + 1]))
            {
                odp = max(odp, pref3[startp] + (pref3[n] - pref3[koniecb + 1]) + pref1[startp] + (pref1[n] - pref1[koniecb + 1]) + min(pref2[startp] + (pref2[n] - pref2[koniecb + 1]), k - (pref1[startp + t] - pref1[startp]) - (pref2[startp + t] - pref2[startp]) - (pref1[koniecb + 1] - pref1[koniecb - t + 1]) - (pref2[koniecb + 1] - pref2[koniecb - t + 1]) - pref1[startp] - (pref1[n] - pref1[koniecb + 1])));
            }
        }
    }
    cout << odp << endl;
    return 0;
}