#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x, y;
  char a;
  cin >> n >> x >> y;
  y++;
  int count = 0;
  for (int i = 1; i <= n - x; i++) {
    cin >> a;
  }
  for (int i = n - x + 1; i < n - y + 1; i++) {
    cin >> a;
    if (a == '1') count++;
  }
  cin >> a;
  if (a == '0') count++;
  for (int i = n - y + 2; i <= n; i++) {
    cin >> a;
    if (a == '1') count++;
  }
  cout << count;
  return 0;
}
