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#include <bits/stdc++.h>
using namespace std;
int main()
{
    cin.tie(0)->sync_with_stdio(0);
    int n,k,t;
    cin>>n>>k>>t;
    vector <int> typ(n+2),pref(n+2,0),suf(n+2,0),prb(n+2,0),sub(n+2,0);
    for(int i=1;i<=n;i++)
    {
        char a;
        cin>>a;
        typ[i]=a-'0';
    }
    for(int i=1;i<=n;i++)
    {
        if(i>1)
        {
            pref[i]=pref[i-1];
            prb[i]=prb[i-1];
            suf[n-i+1]=suf[n-i+2];
            sub[n-i+1]=sub[n-i+2];
        }
        if(typ[i]==2) pref[i]++;
        if(typ[i]==1) {prb[i]++; pref[i]++;}
        if(typ[n-i+1]==2) suf[n-i+1]++;
        if(typ[n-i+1]==1) {sub[n-i+1]++; suf[n-i+1]++;}
    }
    //for(int i=0;i<n+2;i++) cout<<pref[i]<<" "<<prb[i]<<" "<<suf[i]<<" "<<sub[i]<<"\n";
    int maksiu=-1;
    if(prb[n]<=k) {maksiu=n-max(0,pref[n]-k);} ///jak moga same zdalne byc+
    for(int i=t+1;i<=n-t;i++)
        for(int j=i;j<=n-t;j++)
        if(prb[i-1]+sub[j+1]<=k)  ///te niezdalne
        {
            int ls=pref[i-1]-pref[i-1-t]+suf[j+1]-suf[j+t+1];  ///te na trasie
            if(ls<=k)
            {
                int zs=pref[i-1-t]+suf[j+t+1];  ///te w domu
                zs=max(zs-(k-ls),0);
                maksiu=max(maksiu,n-(j-i+1)-2*t-zs);
            }
        }
    cout<<maksiu<<"\n";
}