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#include <bits/stdc++.h>

#define rep(i, j, k) for (int i = (j); i <= (k); ++i)
#define per(i, j, k) for (int i = (j); i >= (k); --i)
#define SZ(v) int((v).size())
#define ALL(v) (v).begin(),(v).end()
#define fi first
#define se second
using ll = long long;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;

template<class T> void chkmn(T &x, T y) { if (y < x) x = y; }
template<class T> void chkmx(T &x, T y) { if (y > x) x = y; }

using namespace std;

const int maxn = 10010;

int n, k, t, a[maxn], cnt[maxn][3];
string str;

int main() {
  cin.tie(nullptr) -> ios::sync_with_stdio(false);
  cin >> n >> k >> t >> str;
  rep (i, 1, n) a[i] = str[i - 1] - '1';
  rep (i, 1, n) rep (j, 0, 2) cnt[i][j] = cnt[i - 1][j] + (a[i] == j);
  int ans = -1;
  rep (l1, 1, n - t + 1) rep (l2, l1 + t, n - t + 1) {
    int r1 = l1 + t - 1, r2 = l2 + t - 1, ban = 0;
    ban += cnt[r1][0] - cnt[l1 - 1][0] + cnt[r1][1] - cnt[l1 - 1][1];
    ban += cnt[r2][0] - cnt[l2 - 1][0] + cnt[r2][1] - cnt[l2 - 1][1];
    ban += cnt[l1 - 1][0] + cnt[n][0] - cnt[r2][0];
    if (ban > k) continue;
    int rest = 0, hw = 0;
    rest += cnt[l1 - 1][2] + cnt[n][2] - cnt[r2][2] + cnt[l1 - 1][0] + cnt[n][0] - cnt[r2][0];
    hw += cnt[l1 - 1][1] + cnt[n][1] - cnt[r2][1];
    chkmx(ans, rest + min(hw, k - ban));
  }
  if (cnt[n][0] <= k) chkmx(ans, cnt[n][2] + cnt[n][0] + min(cnt[n][1], k - cnt[n][0]));
  cout << ans << '\n';
}