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#include<bits/stdc++.h>

using namespace std;

const int MAXN = 8e3 + 7;
int prefd[MAXN];
int prefb[MAXN];

int32_t main(){
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	int n, k, t;
	cin >> n >> k >> t;

	int z = 0;
	for(int i = 1; i <= n ; i++){
		char typc;
		cin >> typc;
		int typ = typc-'0';
		if(typ == 1){
			prefb[i] = 1;
			z++;
		}
		else if(typ == 2){
			prefd[i] = 1;
			z++;
		}
		prefb[i] += prefb[i-1];
		prefd[i] += prefd[i-1];
	}
	int wynik = -1;
	if(prefd[n] >= z-k){
		wynik = n-max(0, z-k);
		cout << wynik << "\n";
		return 0;
	}
	int zd = prefd[n];
	int zad, a, b;
	for(int i = t; i <= n ; i++){
		for(int j = i; j+t <= n ; j = j+1){
			zad = z-k -prefb[j]+prefb[i-1]-prefd[j]+prefd[i-1];
			a = i-t-1;
			b = j+t+1;
			if(a > -1 && b < n+2 && prefd[a]+zd-prefd[b-1] >= zad){
				wynik = max(wynik, a+(n-b+1)-max(0, zad));
			}
		}
	}
	cout << wynik << "\n";
	return 0;
}