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#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define vc vector
#define st first
#define nd second
#define pll pair<ll, ll>
#define sz(a) (ll)a.size()
#define all(a) a.begin(), a.end()
#define pu push
#define pub push_back
#define pob pop_back
#define em emplace
#define emb emplace_back
const ll INF = 2e18;

void program() {
	ll n, m, t;
	cin >> n >> m >> t;
	string str;
	cin >> str;
	ll cnt = 0;
	for (ll i = 0; i < n; i++)
		cnt += str[i] <= '2';
	m = max(0ll, cnt - m);
	ll ans = -1;
	vc<ll> cz(n + 1, 0), cs(n + 1, 0);
	for (ll i = 1; i <= n; i++) {
		cz[i] = cz[i - 1] + (str[i - 1] == '2');
		cs[i] = cs[i - 1] + (str[i - 1] <= '2');
	}
	for (ll i = 0; i + t < n; i++) {
		for (ll j = i + t + 1; j + t - 1 < n; j++) {
			ll a = cz[i] + cz[n] - cz[j + t];
			ll b = i + n - j - t;
			ll c = cs[j] - cs[i + t];
			ll mm = m;
			mm -= c;
			mm = max(mm, 0ll);
			if (mm <= a)
				ans = max(ans, b - mm);
		}
	}
	ll a = 0;
	for (ll i = 0; i < n; i++)
		if (str[i] == '2')
			a++;
	if (a >= m)
		ans = max(ans, n - m);
	cout << ans << "\n";
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	program();
	return 0;
}