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

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n, k, t;
    cin >> n >> k >> t;
    string s;
    cin >> s;
    vector<int> p1 (n+2, 0), p2 (n+2, 0), p3 (n+2, 0), l1 (n+2, 0), l2 (n+2, 0), l3 (n+2, 0), sp (n+2, 0);
    for (int i = 1; i <= n; i++) {
        p1[i] = p1[i-1];
        p2[i] = p2[i-1];
        p3[i] = p3[i-1];
        if (s[i-1] == '1') {
            p1[i]++;
            p3[i]++;
        }
        if (s[i-1] == '2') {
            p2[i]++;
        }
        if (s[i-1] == '3') {
            p3[i]++;
        }
        sp[i] = sp[i-1];
        if (s[i-1] == '1' || s[i-1] == '2') {
            sp[i]++;
        }
    }
    for (int i = n; i > 0; i--) {
        l1[i] = l1[i+1];
        l2[i] = l2[i+1];
        l3[i] = l3[i+1];
        if (s[i-1] == '1') {
            l1[i]++;
            l3[i]++;
        }
        if (s[i-1] == '2') {
            l2[i]++;
        }
        if (s[i-1] == '3') {
            l3[i]++;
        }
    }
    int w = -1;
    for (int i = 1; i <= n; i++) {
        for (int j = i+2*t; j <= n; j++) {
            int x = p3[i-1]+l3[j+1];
            int y = sp[i+t-1]-sp[i-1]+sp[j]-sp[j-t]+p1[i-1]+l1[j+1];
            int z = p2[i-1]+l2[j+1];
            if (y <= k) {
                w = max(w, x+min(k-y, z));
            }
        }
    }
    int x = p3[n], y = p1[n], z = p2[n];
    if (y <= k) {
        w = max(w, x+min(k-y, z));
    }
    cout << w << '\n';
}