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