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

#define rep(i, a, b) for (int i = (a); i < (b); i++)
#define all(x) begin(x), end(x)
#define sz(x) int((x).size())
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

#ifdef LOCAL
auto operator<<(auto& o, auto x) -> decltype(x.first, o);
auto operator<<(auto& o, auto x) -> decltype(x.end(), o) {
  o << "{";
  for (int i = 0; auto y : x) o << ", " + !i++ * 2 << y;
  return o << "}"; }
auto operator<<(auto& o, auto x) -> decltype(x.first, o) {
  return o << "(" << x.first << ", " << x.second << ")"; }
void __print(auto... x) { ((cerr << x << " "), ...) << endl; }
#define debug(x...) __print("[" #x "]:", x)
#else
#define debug(...) 2137
#endif

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

  int n, k, t;
  cin >> n >> k >> t;
  string s;
  cin >> s;
  s = "$" + s;
  vector pref(n + 1, vector<int>(3));
  for(int i = 1; i <= n; i++) {
    for(int j = 0; j < 3; j++) pref[i][j] += pref[i - 1][j];
    pref[i][s[i] - '1']++;
  }

  auto get = [&](int l, int r, int i) {
    if(l < 0) return pref[r][i];
    return pref[r][i] - pref[l][i];
  };

  int res = -1;
  int skip = get(-1, n, 0);
  if(skip <= k) {
    int dist = get(-1, n, 1);
    res = min(k - skip, dist) + n - dist;
  }

  for(int i = 0; i < n; i++) {
    for(int j = i + t; j + t <= n; j++) {
      int skip = get(-1, i, 0) + get(j + t, n, 0);
      skip += get(i, i + t, 0) + get(i, i + t, 1);
      skip += get(j, j + t, 0) + get(j, j + t, 1);
      if(skip > k) continue;
      int tot = i + n - j - t;
      int dist = get(-1, i, 1) + get(j + t, n, 1);
      res = max(res, min(k - skip, dist) + tot - dist);
    }
  }
  cout << res << endl;
}