#include <bits/stdc++.h>
using namespace std;
int main() {
  int *n = new int, x, y;
  cin >> *n >> x >> y;
  delete n;
  n = nullptr;
  string str;
  cin >> str;
  int count = 0;
  if (str[str.length() - y - 1] == '0') {
    str[str.length() - y - 1] = '1';
    count++;
  }
  for (int i = str.length() - x; i < str.length(); i++) {
    if (str[i] == '1' && i != str.length() - y - 1) {
      str[i] = '0';
      count++;
    }
  }
  cout << count;
  return 0;
}
