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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

const int N = 8080;
int n, k, t;
string s;
int p[3][N];

int main() {
  cin.tie(0)->sync_with_stdio(0);
  cin >> n >> k >> t >> s;
  rep(i, 0, 3) rep(j, 0, n) p[i][j + 1] = p[i][j] + (s[j] - '1' == i);
  int trzeba = max(0, n - p[2][n] - k);
  int odp = -1;
  rep(i, 0, n) rep(j, i, n) {
    if (i >= t && n - 1 - j >= t) {
      int tak = (j - i + 1) - (p[2][j + 1] - p[2][i]);
      int moze = (p[1][i - t] - p[1][0]) + (p[1][n] - p[1][j + t + 1]);
      int reszta = i - t + n - 1 - (j + t);
      int wez = min(moze, max(0, trzeba - tak));
      moze -= wez; reszta -= wez; tak += wez;
      if (tak >= trzeba) {
        odp = max(odp, reszta);
      }
    }
  }
  int moze = p[1][n] - p[1][0];
  if (moze >= trzeba) {
    odp = max(odp, n - trzeba);
  }
  cout << odp << '\n';
}