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#include <iostream>
#include <vector>
using namespace std;
struct Count : vector< int > {
  Count(int v, string const &s) : vector< int >(1 + s.size()) {
    int i, c = 0;
    for (i = 0; i < (int)s.size(); ++i)
      (*this)[1 + i] = (c += (s[i] == v));
  }
  int count(int from, int to) const {
    return (*this)[to] - (*this)[from];
  }
  int count() const {
    return (*this)[this->size() - 1];
  }
};
struct Pra {
  int n, k, t;
  Count c1, c2, c3;
  Pra(int n, int k, int t, string const &s)
      : n(n), k(k), t(t), c1('1', s), c2('2', s), c3('3', s) {
  }
  int solve() const {
    if (k >= c1.count())
      return n - (c2.count() - min(c2.count(), k - c1.count()));
    int result = -1;
    int start = 0;
    while (start + t + t <= n) {
      int end = start + t;
      while (++end + t <= n)
        result = max(result, solve(start, end));
      ++start;
    }
    return result;
  }
  int solve(int start, int stop) const {
    int c1_skipped = c1.count(0, start + t) + c1.count(stop, n);
    int c2_skipped = c2.count(start, start + t) + c2.count(stop, stop + t);
    int c2_skip = k - (c1_skipped + c2_skipped);
    if (c2_skip < 0)
      return -1;
    int count = c1.count(0, start) + c1.count(stop + t, n) + c3.count(0, start) + c3.count(stop + t, n);
    int c2_count = c2.count(0, start) + c2.count(stop + t, n);
    if (c2_skip > c2_count)
      c2_skip = c2_count;
    count += c2_skip;
    return count;
  }
};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, k, t;
  string s;
  cin >> n >> k >> t >> s;
  cout << Pra(n, k, t, s).solve() << '\n';
}