#include <bits/stdc++.h>
using namespace std;
int main() {
  long int n, x, y;
  int operations = 0;
  cin >> n >> x >> y;
  char a[n];
  cin >> a;
  for (int l = n - x; l < n; l++) {
    if (l == n - 1 - y && a[l] != '1')
      operations++;
    else if (l != n - 1 - y && a[l] != '0')
      operations++;
  }
  cout << operations;
  return 0;
}
