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/*
 * Author: toko
 * Time: 2025-03-10 12:28:47
 */

#ifndef DEBUG
#define NDEBUG
#pragma GCC optimize("Ofast,unroll-loops")
#endif

#include <iostream>
#include <cstdint>
#include <vector>
#include <algorithm>
#include <array>
using namespace std;

int main()
{
	iostream::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);

	uint32_t n, k, t;
	cin >> n >> k >> t;
	string s;
	cin >> s;
	uint32_t b = (uint32_t) count(s.begin(), s.end(), '1');
	if (k > b)
	{
		k -= b;
		uint32_t ans = 0;
		for (auto& c : s)
		{
			if (c == '2')
			{
				if (k > 0)
				{
					k--;
					ans++;
				}
			}
			else
				ans++;
		}
		cout << ans << endl;
		return 0;
	}

	vector<array<uint32_t, 3>> p(n + 1, { 0, 0, 0 });

	for (uint32_t i = 0; i < n; i++)
	{
		p[i + 1] = p[i];
		p[i + 1][s[i] - '1']++;
	}
	uint32_t maxi = -1u;
	uint32_t maxii = -1u;
	uint32_t maxij = -1u;
	for (uint32_t i = 0; i + t <= n; i++)
	{
		for (uint32_t j = i + t; j + t <= n; j++)
		{
			uint32_t m = p[n][1] + p[n][0] - k;
			uint32_t o = p[j][0] + p[j][1] - p[i + t][0] - p[i + t][1];
			if (m < o)
				m = 0;
			else
				m -= o;
			uint32_t h = p[i][1] + p[n][1] - p[j + t][1];
			if (h < m)
				continue;
			uint32_t f = i + n - (j + t) - m;
			if (maxi == -1u || f >= maxi)
			{
				maxi = f;
				maxii = i;
				maxij = j;
			}
		}
	}
	if (maxi == -1u)
		cout << -1 << endl;
	else
		cout << maxi << endl;
	cerr << maxii << ' ' << maxij << endl;
	return 0;
}