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#include<bits/stdc++.h>
using namespace std;
const int INF=1e9+1;
char tab[8009];
int pref1[8009];
int pref2[8009];
int pref3[8009];
int suma(int a, int b, int *pref)
{
    return pref[b]-pref[a-1];
}
int main()
{ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int n,k,t;
    cin>>n>>k>>t;
    for(int i=1;i<=n;i++)
    {
        cin>>tab[i];
        pref1[i]=pref1[i-1];
        pref2[i]=pref2[i-1];
        pref3[i]=pref3[i-1];
        if(tab[i]=='1'){pref1[i]++;}
        if(tab[i]=='2'){pref2[i]++;}
        if(tab[i]=='3'){pref3[i]++;}
    }
    int wyn=-INF;
    if(suma(1,n,pref1)<=k)
    {
        wyn=suma(1,n,pref1)+suma(1,n,pref3)+min(k-suma(1,n,pref1),suma(1,n,pref2));
    }
    for(int i=t+1;i<=n-t;i++)
    {
        for(int j=i;j<=n-t;j++)
        {
            int skipp=0,w=0,w2=0;
            skipp+=suma(i-t,i-1,pref1)+suma(i-t,i-1,pref2);
            skipp+=suma(j+1,j+t,pref1)+suma(j+1,j+t,pref2);
            skipp+=suma(1,i-t-1,pref1)+suma(j+t+1,n,pref1);
            w+=suma(1,i-t-1,pref1)+suma(j+t+1,n,pref1);
            w+=suma(1,i-t-1,pref3)+suma(j+t+1,n,pref3);
            w2+=suma(1,i-t-1,pref2)+suma(j+t+1,n,pref2);
            if(skipp>k){continue;}
            wyn=max(wyn,w+min(k-skipp,w2));
        }
    }
    cout<<max(wyn,-1)<<'\n';
    return 0;
}