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#include <bits/stdc++.h>
using namespace std;

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	int n, k, t;
	cin >> n >> k >> t;
	string s;
	cin >> s;
	s = '3' + s;
	int px1[n+1], px2[n+1], px3[n+1];
	px1[0] = 0;
	px2[0] = 0;
	px3[0] = 0;
	for(int i = 1; i <= n; i++){
		px1[i] = px1[i-1];
		px2[i] = px2[i-1];
		px3[i] = px3[i-1];
		if(s[i] == '1') px1[i]++;
		else if(s[i] == '2') px2[i]++;
		else px3[i]++;
		
		if(s[i] != '1') continue;
		if(i > t & i + t <= n) continue;
		cout << -1;
		return 0;
	}
	if(px1[n] <= k){
		cout << min(px3[n] + k, n);
		return 0;
	}
	int maxGoHome = n - t;
	int maxResult = 0;
	int len;
	int k1 = k;
	for(int i = t+1; i <= maxGoHome; i++){
		for(int j = i; j <= maxGoHome; j++){
			len = px1[i-1] + px1[n] - px1[j] + px2[i-1] - px2[i-t-1] + px2[j+t] - px2[j];
			if(len > k) continue;
			k1 = k;
			k1 -= (px1[i-1] - px1[i-t-1] + px1[j+t] - px1[j] + px2[i-1] - px2[i-t-1] + px2[j+t] - px2[j]);
			len = min(px3[i-t-1] + px3[n] - px3[j+t] + k1, n - j + i - 1);
			maxResult = max(maxResult, len);
			break;
		}
	}
	cout << maxResult;
	return 0;
}