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// Author: Olaf Surgut (surgutti)
// Created on 10-03-2025 12:25:35
#include "bits/stdc++.h"
using namespace std;

// #define int long long
#define ll long long
#define ld long double

#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define eb emplace_back
#define sz(x) (int)(x).size()
#define all(x) begin(x),end(x)
#define FOR(i,l,r) for(int i=(l);i<=(r);i++)
#define ROF(i,r,l) for(int i=(r);i>=(l);i--)

auto& operator<<(auto &o, pair<auto, auto> p) {
	return o << "(" << p.st << ", " << p.nd << ")";}
auto operator<<(auto &o, auto x)->decltype(end(x), o) {
	o << "{"; int i=0; for (auto e : x) o << ","+!i++ << e;
	return o << "}";}

#ifdef LOCAL
#define debug(x...) cerr << "[" #x "]: ", [](auto...$) { \
	((cerr << $ << "; "),...) << endl; }(x)
#else
#define debug(...)
#endif

#define rep(i,a,b) for(int i = a; i < (b); i++)
using pii = pair<int, int>;
using vi = vector<int>;

const int N = 8000 + 7;

int n, k, t;
string s;

int pref[3][N];
int suff[3][N];

signed main() {
	cin.tie(0)->sync_with_stdio(0);

	cin >> n >> k >> t;
	cin >> s;
	s = '#' + s;

	rep(i, 0, 3) {
		FOR(j, 1, n) {
			pref[i][j] = pref[i][j - 1] + (s[j] == char(i + '1'));
		}

		ROF(j, n, 1) {
			suff[i][j] = suff[i][j + 1] + (s[j] == char(i + '1'));
		}
	}

	k = max(0, pref[0][n] + pref[1][n] - k);
	
	int ans = -1;
	if (pref[1][n] >= k) {
		ans = max(ans, n - k);
	}

	FOR(i, 1, n) {
		FOR(j, i + 2 * t, n) {
			int left = max(0, k - (j - i - 2 * t + 1 - pref[2][j - t] + pref[2][i + t - 1]));
			if (pref[1][i - 1] + suff[1][j + 1] >= left) {
				ans = max(ans, i - 1 + n - j - left);
			}
		}
	}

	cout << ans << '\n';

	return 0;
}