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#include <bits/stdc++.h>
using namespace std;
#define _upgrade ios_base::sync_with_stdio(0), cout.setf(ios::fixed), cout.precision(10), cin.tie(0), cout.tie(0);
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define fwd(i, a, b) for (int i = (a); i < (b); ++i)
#define all(c) (c).begin(), (c).end()
#define sz(X) (int)((X).size())
#ifdef LOCAL
ostream &operator<<(ostream &out, string str) {
   for (char c : str)
      out << c;
   return out;
}
template <class L, class R> ostream &operator<<(ostream &out, pair<L, R> p) { return out << "(" << p.st << ", " << p.nd << ")"; }
template <class L, class R, class S> ostream &operator<<(ostream &out, tuple<L, R, S> p) {
   auto &[a, b, c] = p;
   return out << "(" << a << ", " << b << ", " << c << ")";
}
template <class T> auto operator<<(ostream &out, T a) -> decltype(a.begin(), out) {
   out << '{';
   for (auto it = a.begin(); it != a.end(); it = next(it))
      out << (it != a.begin() ? ", " : "") << *it;
   return out << '}';
}
void dump() { cerr << "\n"; }
template <class T, class... Ts> void dump(T a, Ts... x) {
   cerr << a << ", ";
   dump(x...);
}
#define debug(...) cerr << "[" #__VA_ARGS__ "]: ", dump(__VA_ARGS__)
#else
#define debug(...) 42
#endif

array<int, 8008> tab[3];

// sum in [a,b]
int sum(int t, int a, int b) { return b < a ? 0 : (tab[t][b] - (a ? tab[t][a - 1] : 0)); }
int sum01(int a, int b) { return sum(0, a, b) + sum(1, a, b); }

int32_t main() {
   _upgrade;
   int n, k, t;
   cin >> n >> k >> t;
   debug(n, k, t);
   string s;
   cin >> s;

   rep(i, sz(s)) tab[s[i] - '1'][i]++;
   rep(i, 3) partial_sum(all(tab[i]), tab[i].begin());

   int ans = -1;

   if (sum(0, 0, n - 1) <= k)
      ans = n - max(0, sum01(0, n - 1) - k);
   debug(ans);

   rep(i, n) fwd(j, i + 2 * t, n) {

      int pominiete = sum01(i, i + t - 1) + sum01(j - t + 1, j);
      int w_biurze = sum(0, 0, n - 1) - sum(0, i, j);
      debug(i, j, pominiete, w_biurze);

      if (pominiete + w_biurze <= k) {
         int zdalnie = sum01(0, n - 1) - sum01(i, j);
         int wolne = sum(2, 0, n - 1) - sum(2, i, j);
         int x = wolne + min(k - pominiete, zdalnie);
         debug(i, j, x);
         ans = max(ans, x);
      }
   }
   cout << ans << endl;
}