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#include "bits/stdc++.h"
using namespace std;
#define all(x) x.begin(),x.end()
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << p.first << " " << p.second; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { string sep; for (const T &x : v) os << sep << x, sep = " "; return os; }
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#define ASSERT(...) 42
#endif
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pi;
const int oo = 1e9;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n,k,t; cin >> n >> k >> t;
    string s; cin >> s;
    vi meeting(n+1);
    vi office(n+1);
    for(int i=0;i<n;++i) {
        meeting[i+1]=meeting[i]+ (s[i]<'3');
        office[i+1]=office[i]+(s[i]=='1');
    }
    int ans=-1;
    // not going to work
    if(office[n]<=k) {
        int skipmaybe = meeting[n]-office[n];
        int use = min(skipmaybe,k-office[n]);
        ans=max(ans,use+n-meeting[n] + office[n]);
    }
    for(int i=0;i+t<=n;++i) {

        for(int j=i+t;j+t<=n;++j) {
            int skip=0;
            auto travel = [&](int x) {
                skip+=meeting[x+t]-meeting[x];
            };
            travel(i),travel(j);
            auto opts = [&](int l, int r) {
                return meeting[r]-meeting[l] - (office[r]-office[l]);
            };
            auto freetime = [&](int l, int r) {
                return (r-l) - (meeting[r] - meeting[l]) + (office[r]-office[l]);
            };

            skip+=office[i];
            skip+=office[n]-office[j+t];
            if(skip<=k) {
                int skipmaybe = opts(0,i) + opts(j+t,n);
                int use = min(skipmaybe,k-skip);
                ans=max(ans, use  + freetime(0,i) + freetime(j+t,n));
            }
        }
    }
    cout << ans << '\n';
}