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#include<cstdio>
#include<vector>
#include<algorithm>

using namespace std;

int main() {
  int n, k, t; scanf(" %d %d %d", &n, &k, &t);
  char s[8002]; scanf(" %s", s);

  vector<int> v1(n+1, 0), v2(n+1, 0);

  for (int i=0; i<n; ++i) {
    v1[i+1] = v1[i];
    v2[i+1] = v2[i];
    if (s[i] == '1') {
      v1[i+1]++;
    }
    if (s[i] == '2') {
      v2[i+1]++;
    }
  }
/*
  for (int i=0; i<n+1; ++i) printf("%d ", v1[i]);
  printf("\n");
  for (int i=0; i<n+1; ++i) printf("%d ", v2[i]);
  printf("\n");
*/
  int res = -1;
  if (v1[n] <= k) res = n - max(0, v1[n] + v2[n] - k);

  for (int i=t; i<n; ++i) {
    int lost1 = v1[i] + v2[i] - v2[i-t];
//    printf("Dojezdzam: %d, przegapiam: %d\n", i, lost1);

    for (int j=i; j<=n-t; ++j) {
      int lost2 = v1[n] - v1[j] + v2[j+t] - v2[j];
//      printf("Wyjezdzam %d, przegapiam: %d\n", j, lost2);
      
      int lost = lost1 + lost2;
      if (lost <= k) {
        int now = i-t + (n-j-t) - max(0, v2[i-t] + v2[n] - v2[j+t] - (k - lost));
//        printf("Przegapiam tylko: %d. Licze: %d!\n", lost, now);
        res = max(res, now);
      }
    }
  }

  printf("%d\n", res);
  return 0;
}