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#include<bits/stdc++.h>

using namespace std;

typedef long long ll;

void solve() {
    ll n,k,t;
    cin>>n>>k>>t;
    string s;
    cin>>s;
    ll lost=0, c=0;
    vector <vector <ll> > pref(n, vector <ll> (3,0)), suf(n, vector <ll> (3,0));
    pref[0][s.front()-'1']++;
    if(s.front()=='1') {
        c++;
    }
    for(ll i=1;i<n;i++) {
        for(ll j=0;j<3;j++) {
            pref[i][j]=pref[i-1][j];
        }
        pref[i][s[i]-'1']++;
        if(s[i]=='1') {
            c++;
        }
    }
    suf[n-1][s.back()-'1']++;
    for(ll i=n-2;i>=0;i--) {
        for(ll j=0;j<3;j++) {
            suf[i][j]=suf[i+1][j];
        }
        suf[i][s[i]-'1']++;
    }
    ll all=pref[n-1][0]+pref[n-1][1];
    ll res=n-max(0ll, all-k);
    if(pref[n-1][0]>k) {
        res=0;
    }
    bool czy=0;
    for(ll i=t;i<n;i++) {
        for(ll j=i;j<n-t;j++) {
            ll lost=pref[i-1][0]+pref[i-1][1]+suf[j+1][0]+suf[j+1][1];
            ll tmp=i-t+(n-1-(j+t));
            //cout<<tmp<<"\n";
            ll rest=0;
            if(i-t-1>=0) {
                lost-=pref[i-t-1][1];
                rest+=pref[i-t-1][1];
            }
            if(j+t+1<n) {
                lost-=suf[j+t+1][1];
                rest+=suf[j+t+1][1];
            }
            //cout<<i<<" "<<j<<" "<<lost<<"\n";
            //cout<<tmp<<"\n";
            if(lost>k) {
                continue;
            }
            else {
                czy=1;
            }
            ll p=k-lost;
            tmp-=max(0ll, rest-p);
            res=max(res, tmp);
        }
    }
    if(!czy) {
        cout<<"-1\n";
        return;
    }
    cout<<res<<"\n";
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    solve();
}