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#include <bits/stdc++.h>
using namespace std;
int n, k, t, res = -1;
int sum[4];
int const N_max=8000;
string s;
vector <int> path;
int pref_1[N_max];
int suff_1[N_max];
int pref_free[N_max];
int suff_free[N_max];
//pref && suff for 2;
int twos_from_left[N_max];
int twos_from_right[N_max];
void convert_path(){
    for (int i=0; i<n; i++){
        int num=s[i]-'0';
        path.push_back(num);
        sum[num]++;
    }
    return;
}
void fill_arrays(){
    if (path[0]==1){pref_1[0]=1;}
    for (int i=1; i<n; i++){
        if (path[i]==1){
            pref_1[i]=pref_1[i-1]+1;
        }
        else{pref_1[i]=pref_1[i-1];}
        
        if (path[i-1]==3){
            pref_free[i]=pref_free[i-1]+1;
        }
        else{pref_free[i]=pref_free[i-1];}
    }
    
    if (path[n-1]==1){suff_1[n-1]=1;}
    for(int i=n-1; i>=0; i--){
        if (path[i]==1){
            suff_1[i]=suff_1[i+1]+1;
        }
        else{suff_1[i]=suff_1[i+1];}
        
        if (path[i+1]==3){
            suff_free[i]=suff_free[i+1]+1;
        }
        else{suff_free[i]=suff_free[i+1];}
    }
    /*for (int i=0; i<n; i++){
        pref_1[i]=suff_1[n-1-i];
        pref_free[i]=suff_free[n-1-i];
    }*/
    
    int tfr_t=0;
    for(int i=n-1; i>n-1-t; i--){if(path[i]==2){tfr_t++;}}
    twos_from_right[n-t]=tfr_t;
    for (int i=n-t - 1; i>=0; i--){
        int act=twos_from_right[i+1];
        if (path[i]==2){act++;}
        if (path[i+t]==2){act--;}
        twos_from_right[i]=act;
    }
    
    int tfl_t=0;
    for(int i=0; i<t; i++){if(path[i]==2){tfl_t++;}}
    twos_from_left[t-1]=tfl_t;
    for (int i=t; i<n; i++){
        int act=twos_from_left[i-1];
        if (path[i]==2){act++;}
        if (path[i-t]==2){act--;}
        twos_from_left[i]=act;
    }
    return;
}
int find_result(int left, int right){
    int mm=pref_1[left+t-1]+suff_1[right-t+1]+twos_from_right[left]+twos_from_left[right];
    //if (left==3 && right==7){cout<<"\n"<<mm; exit(0);}
    if (mm>k){return -1;}
    //if (left==3 && right==7){cout<<"\n"<<pref_free[left]+suff_free[right]; exit(0);}

    return pref_free[left]+suff_free[right]+ (k-mm);
}
void debug(){
    cout<<"pref_1"<<"\n";
    for(int i=0; i<n; i++){cout<<pref_1[i]<<" ";}
    cout<<"\n"<<"suff_1"<<"\n";
    for(int i=0; i<n; i++){cout<<suff_1[i]<<" ";}
    cout<<"\n"<<"pref_free\n";
    for(int i=0; i<n; i++){cout<<pref_free[i]<<" ";}
    cout<<"\n"<<"suff_free\n";
    for(int i=0; i<n; i++){cout<<suff_free[i]<<" ";}
    cout<<"\n"<<"twos_from_left\n";
    for(int i=0; i<n; i++){cout<<twos_from_left[i]<<" ";}
    cout<<"\n"<<"twos_from_right\n";
    for(int i=0; i<n; i++){cout<<twos_from_right[i]<<" ";}
}
int main()
{   
    cin>>n>>k>>t;
    cin>>s;
    convert_path();
    fill_arrays();
    if (k>=sum[1]+sum[2]){cout<<s.size(); return 0;}
    pair <int, int> lr={-1, -1};
    //debug(); 
    //return 0;
    for (int i=0; i<n-t; i++){
        for(int j=i+(2*t); j<n; j++){
            if (res<find_result(i, j)){
                lr={i, j};
                res=find_result(i, j);
            }
        }
    }
    cout<<res;
    //cout<<"\n"<<find_result(3, 7);
    //cout<<"\n"<<lr.first<<" "<<lr.second;
    return 0;
}