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#include<bits/stdc++.h>
#define FOR(i,a,b) for(int i=a;i<(int)b;++i)
#define FORD(i,a,b) for(int i=a;i>=(int)b;--i)
#define PB push_back
#define EB emplace_back
#define FI first
#define SE second
#define umap unordered_map
#define uset unordered_set
#define vi vector<int>
#define vvi vector<vi>
#define vll vector<ll>
#define vvll vector<vll>
#define vpii vector<pii>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define ALL(X) (X).begin(),(X).end()
#ifndef DEBUG
#define endl (char)10
#endif
using namespace std;
using ll = long long;
using ld = long double;

template <class T>
istream& operator>> (istream& is, vector<T>& vec){
    FOR(i,0,vec.size()) is >> vec[i];
    return is;
}
template <class T>
ostream& operator<< (ostream& os, vector<T>& vec){
    for(auto& t : vec) os << t << " ";
    return os;
}
template<class T, class U>
ostream& operator<< (ostream& os, const pair<T, U>& p){
    os << p.FI << " " << p.SE;
    return os;
}
template<class T, class U>
istream& operator>> (istream& is, pair<T, U>& p){
    is >> p.FI >> p.SE;
    return is;
}

int main () {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n, k, d;
    string s;
    cin >> n >> k >> d >> s;
    int ile = 0;
    FOR(i,0,n) if (s[i] == '1') ile++;
    if (ile <= k) {
        FOR(i,0,n) if (s[i] == '2') ile++;
        cout << n - max(0, ile - k) << endl;
        return 0;
    }
    vi ps1(n + 1), ps2(n + 1);
    ps1[0] = ps2[0] = 0;
    FOR(i,0,n){
        ps1[i + 1] = ps1[i] + (s[i] == '1');
        ps2[i + 1] = ps2[i] + (s[i] == '2');
    }
    auto get12 = [&ps1, &ps2](int a, int b) {
        return ps1[b] + ps2[b] - ps1[a] - ps2[a];
    };
    auto get1 = [&ps1](int a, int b) {
        return ps1[b] - ps1[a];
    };

    int ans = -1;
    FOR(a,0,n - 2 * d){
        FOR(b,a+d,n-d+1) {
            int c = get12(a, a+d) + get12(b, b + d);
            if (c <= k) {
                int cc = get1(0, a) + get1(b+d, n);
                if (cc <= k - c) {
                    int ccc = get12(0, a) + get12(b+d, n);
                    ans = max(ans, n - (b + d - a) - max(0, ccc - (k - c)));
                }
            }
        }
    }
    cout << ans << endl;
}