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

#define rep(i, b, e) for (int i = (b); i <= (e); i++)
#define per(i, b, e) for (int i = (e); i >= (b); i--)
#define FOR(i, b, e) rep(i, b, (e)-1)
#define SZ(x) int(x.size())
#define all(x) x.begin(), x.end()
#define pb push_back
#define mp make_pair
#define st first
#define nd second
using ll = long long;
using vi = vector<int>;
using pii = pair<int, int>;

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 << ", " + 2 * !i++ << e;
  return o << "}";
}
#ifdef LOCAL
#define deb(x...)                       \
  cerr << "[" #x "]: ", [](auto... $) { \
    ((cerr << $ << "; "), ...) << endl; \
  }(x)
#else
#define deb(...)
#endif

const int N = 8004;
int pref1[N];
int pref2[N];

int ile1(int a, int b) {
  if (b < a)
    return 0;
  return pref1[b] - pref1[a - 1];
}

int ile2(int a, int b) {
  if (b < a)
    return 0;
  return pref2[b] - pref2[a - 1];
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie();

  int n, k, t;
  cin >> n >> k >> t;
  string s;
  cin >> s;
  s = " " + s;

  for (int i = 1; i <= n; i++) {
    pref1[i] = pref1[i - 1] + (s[i] == '1');
    pref2[i] = pref2[i - 1] + (s[i] == '2');
  }

  int ans = -1;

  if (ile1(1, n) <= k) {
    int na_ile_musze_isc = max(0, ile2(1, n) - (k - ile1(1, n)));
    ans = n - na_ile_musze_isc;
  }

  for (int i = 1; i <= n - t * 2 + 1; i++) {
    for (int j = i + t; j <= n - t + 1; j++) {
      int ile_opuszcze = ile1(1, i + t - 1) + ile1(j, n) + ile2(i, i + t - 1) +
                         ile2(j, j + t - 1);
      if (ile_opuszcze > k)
        continue;

      int ile_jeszcze_zostalo = ile2(1, i - 1) + ile2(j + t, n);
      int na_ile_musze_isc = max(0, ile_jeszcze_zostalo - (k - ile_opuszcze));

      int cur = n - (j + t - 1 - i + 1) - na_ile_musze_isc;

      ans = max(ans, cur);
    }
  }
  cout << ans << "\n";
}