#include <bits/stdc++.h>
using namespace std;
int main() {
  long n, x, y;
  char s[200010];
  cin >> n >> x >> y;
  cin.ignore();
  cin.getline(s, 200010);
  long front_zeros = 0;
  long back_zeros = 0;
  long zeros = 0;
  for (long i = n - x; i < n; i++) {
    if (s[i] == '0' && i == n - y - 1) {
      zeros++;
    } else if (s[i] == '1' && i == n - y - 1) {
    } else if (s[i] == '1') {
      zeros++;
    }
  }
  cout << zeros << "\n";
  return 0;
}
