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#include <stdio.h>
#include <time.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <map> 
#include <string>
#include <vector>  
#include <iostream> 
#include <sstream> 
#include <queue>
#include <algorithm>
#include <assert.h>


using namespace std;

#define ll long long
#define PB 		push_back
#define FOR(a,start,end) 	for(int a=int(start); a<int(end); a++)
#define INF 		INT_MAX
#define SORT(a) 	sort(a.begin(),a.end()) 
#define CL(a,x) 		memset(a,x,sizeof(a))
#define REP(a,x)	for(int a=0;a<x;a++)
#define REP1(a,x)	for(int a=1;a<=x;a++)
#define MP 		make_pair



typedef vector<ll>     vi;
typedef pair<ll, ll>     pii;
typedef vector<string> vs;
typedef vector<pii> vii;
typedef vector<vector<ll> > vvi;
typedef vector<vector<string> > vvs;
typedef vector<pair<string, string> > vss;
typedef pair<string, string> pss;
typedef pair<ll, pii> ppii;
typedef vector<ppii> vppii;
typedef vector<vector<pii> > vvii;
typedef vector<vvi> vvvi;


ll  n, k, q, d, t, g, b, z, p, a, c, m;

vi vk, va, vb,vc;
vvi vva, vvb, vvd, vva0;
vii vax;
vvii vvqx;
vs vw;
string w;
ll iles(int a, int b) {
	return va[a] - va[b];
}
ll ilez(int a, int b) {
	return vb[a] - vb[b];
}
ll ilej(int a, int b) {
	return vc[a] - vc[b];
}
int main() {
	//freopen("c:\\wojtek\\uva\\pa\\debug\\t1.in", "rt", stdin);
	//freopen("c:\\cygwin64\\home\\plwokow\\.check_sol\\pra\\praMine\\8901.in", "rt", stdin);
	//d = 1000000007;
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(NULL);
	//	while (1) {
	cin >> n>>k>>t;
	cin >> w;
	va.assign(n + 1, 0); vb.assign(n + 1, 0); vc.assign(n + 1, 0);
	for (int i = 1; i <= n; i++) {
		va[i] = va[i - 1];
		vb[i] = vb[i - 1];
		vc[i] = vc[i - 1];
		if (w[i - 1] < '3') {
			va[i]++;
		}
		else
			vb[i]++;
		if (w[i - 1] == '1')
			vc[i]++;
	}
	//
	bool jest = false;
	z = 0;
	if (ilej(n, 0) <= k) {
		ll k2 = iles(n, 0);
		z = n-max(k2-k,0ll);
		jest = true;
	}

	
	for (int i = 0; i < n - (2 * t + 1); i++) {
		ll k1 = iles(t+i, i);
		for (int j = t + i + 1; j <= n - t; j++) {
			ll k2 = iles(t + j, j);
			ll c1 = ilej(i, 0) + ilej(n,t+ j);
			if (k1 + k2+c1 <= k) {
				jest = true;
				ll k4 = k - k1 - k2;
				
				ll k3 = iles(max(0ll, (ll)(i - 1)), 0ll) + iles(n, t + j);
				k3 = min(k4,k3);
				z = max(ilez(i, 0) + ilez(n, t + j)+k3, z);
			}
		}

	}
	if (!jest)
		z = -1;
	cout<<z << '\n';
	//}

	return 0;

}