#include <bits/stdc++.h>
using namespace std;
char a[200005];
int main() {
  int y, x, n, ans = 0;
  cin >> n >> x >> y;
  cin >> a;
  for (int i = n - 1; i >= n - 1 - x; i--) {
    if (i == n - 1 - y && a[i] == '0')
      ans++;
    else if (a[i] == '1' && i != n - 1 - y && i != n - 1 - x)
      ans++;
  }
  cout << ans << endl;
  return 0;
}
