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#include<bits/stdc++.h>
#define st first
#define nd second
#define all(x) x.begin(), x.end()
#define BOOST cin.tie(NULL); ios_base::sync_with_stdio(false);
 
// #define int ll
typedef long long ll;

using namespace std;
template <typename T> struct tag:reference_wrapper <T>{ using reference_wrapper <T>::reference_wrapper; };
template <typename T1, typename T2> static inline tag <ostream> operator<<(tag <ostream> os, pair<T1, T2> const& p){ return os.get()<<"{"<<p.first<<", "<<p.second<<"}", os;}
template <typename Other> static inline tag <ostream> operator<<(tag <ostream> os, Other const& o){ os.get()<<o; return os; }
template <typename T> static inline tag <ostream> operator <<(tag <ostream> os, vector <T> const& v){ os.get()<<"["; for (int i=0; i<v.size(); i++) if (i!=v.size()-1) os.get()<<v[i]<<", "; else os.get()<<v[i]; return os.get()<<"]", os; }
template <typename T> static inline tag <ostream> operator <<(tag <ostream> os, set <T> const& s){ vector <T> v; for (auto i: s) v.push_back(i); os.get()<<"["; for (int i=0; i<v.size(); i++) if (i!=v.size()-1) os.get()<<v[i]<<", "; else os.get()<<v[i]; return os.get()<<"]", os; }

int n, k, t; 
vector<int> p12(n + 2, 0);
vector<int> p2(n + 2, 0);
vector<int> p1(n + 2, 0);

int c12(int l, int r){return p12[r] - p12[l - 1];}
int c1(int l, int r){return p1[r] - p1[l - 1];}
int c2(int l, int r){return p2[r] - p2[l - 1];}

int calc(int sb, int eb){
    int miss = 0;
    int pot = 0;
    int cal2 = 0;
    miss = c1(1, sb - 1) + c12(sb, sb + t - 1) + c12(eb, eb + t - 1) + c1(eb + t, n);
    if(miss > k) return -1;
    pot = sb - 1 - c2(1, sb - 1) + (n - (eb + t - 1)) - c2(eb + t, n);
    cal2 = c2(1, sb - 1) + c2(eb + t, n);
    return pot + min((k - miss), cal2);
}

int32_t main(){
    BOOST;
    cin >> n >> k >> t;
    string day; cin >> day;
    day = "#" + day + "###";
    p12.assign(n + 2, 0);
    p2.assign(n + 2, 0);
    p1.assign(n + 2, 0);
    
    for(int i = 1; i <= n + 1; i++){
        p12[i] = p12[i - 1];
        p2[i] = p2[i - 1];
        p1[i] = p1[i - 1];
        if(day[i] == '1'){
            p12[i]++;
            p1[i]++;
        }
        if(day[i] == '2'){
            p12[i]++;
            p2[i]++;
        }
    }

    int ans = -1;
    if(p12[n] - p2[n] <= k){
        ans = n - max(p12[n] - k, 0);
    }

    for(int i = 1; i <= n; i++){
        for(int j = i + t; j <= n - t + 1; j++){
            ans = max(ans, calc(i,j));
        }
    }
    cout << ans << "\n";
    return 0;
}