#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x, y, c = 0;
  cin >> n >> x >> y;
  string mas;
  cin >> mas;
  for (int i = n - x; i < n; i++) {
    if (i == n - y - 1) {
      if (mas[i] == '0') {
        mas[i] = '1';
        c++;
      }
    } else {
      if (mas[i] == '1') {
        mas[i] = '0';
        c++;
      }
    }
  }
  cout << c;
  return 0;
}
