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#include<iostream>
#include<vector>
#include<utility>
#include<algorithm>
#define ll long long
using namespace std;

vector<vector<int>>tab(4,vector<int>());
int sum_prze(int i, int a, int b){
    if(a>b)return 0;
    if(a==0){
        return tab[i][b];
    }
    return tab[i][b]-tab[i][a-1];
}
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);cout.tie(NULL);
    int n,k,t;
    cin>>n>>k>>t;
    string s;
    cin>>s;
    for(int i = 0;i<4;++i){
        tab[i].resize(s.size(),0);
    }
    for(int i = 0;i<s.size();++i){
        if(i>0){
            for(int j = 0;j<3;++j){
                tab[j+1][i]=tab[j+1][i-1];
            }
        }
        tab[s[i]-'0'][i]++;
    }
    int meet_cnt = sum_prze(1,0,n-1)+sum_prze(2,0,n-1);
    if(k>=meet_cnt){
        cout<<n;
        return 0;
    }
    k = meet_cnt - k;
    int best = -1;
    for(int i = 0;i<n;i++){
        for(int j = i+2;j<n;++j){
            int pocz = i+t;
            int kon = j-t;
            if(pocz>kon){
                continue;
            }
            int cnt = sum_prze(1,pocz,kon)+sum_prze(2,pocz,kon);
            int remain = k-cnt;
            int zoom  = sum_prze(2,0,i-1)+sum_prze(2,j+1,n-1);
            int in_home = i+n-1-j;
            if(remain>zoom){
                continue;
            }
            if(remain<0){
                remain=0;
            }
            if(in_home-remain>best){
                
                best=in_home-remain;
                //cout<<i<<" "<<j<<" "<<best<<endl;
            }
        }
    }
    int zoom2 = sum_prze(2,0,n-1);
    if(zoom2>=k && n-1-k>best){
        best=n-1-k;
        //cout<<0<<" "<<n-1<<" "<<best<<endl;
    }
    cout<<best;
    return 0;
}