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#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,b) for (int i = (a); i <= (b); ++i)
#define REPD(i,a,b) for (int i = (a); i >= (b); --i)
#define FORI(i,n) REP(i,1,n)
#define FOR(i,n) REP(i,0,int(n)-1)
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define vi vector<int>
#define ll long long
#define SZ(x) int((x).size())
#define DBG(v) cerr << #v << " = " << (v) << endl;
#define FOREACH(i,t) for (typeof(t.begin()) i=t.begin(); i!=t.end(); i++)
#define fi first
#define se second

const int N = 8080;

int n,k,t;
char s[N];
int pref_o[N], pref_a[N], suff_o[N], suff_a[N];

int main() {
	scanf("%d%d%d %s", &n, &k, &t, s);
	pref_o[0] = pref_a[0] = 0;
	FOR(i,n) {
		pref_o[i+1] = pref_o[i] + (s[i]=='2');
		pref_a[i+1] = pref_a[i] + (s[i]!='3');
	}
	suff_o[n+1] = suff_a[n+1] = 0;
	REPD(i,n-1,0) {
		suff_o[i+1] = suff_o[i+2] + (s[i]=='2');
		suff_a[i+1] = suff_a[i+2] + (s[i]!='3');
	}
	int all = pref_a[n], need = max(0, all - k);
	int ans = -1;
	if (pref_o[n] >= need) {
		printf("%d\n", n-need);
		return 0;
	}
	FOR(i,n+1) {
		REP(j,i+2*t+1,n+1) {
			int n_before = pref_o[i];
			int n_during = all - pref_a[i+t] - suff_a[j-t];
			int n_after  = suff_o[j];
			//cout << i << " " << j << " " << n_before << " " << n_during << " " << n_after << "\n";
			if (n_before + n_during + n_after >= need) {
				int need_ba = max(0, need-n_during);
				ans = max(ans, i + n+1-j - need_ba);
			}
		}
	}
	printf("%d\n", ans);
	return 0;
}