#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n, x, y;
  string second;
  cin >> n >> x >> y >> second;
  int ans = 0;
  for (int i = n - x; i < n; ++i) {
    if (i == n - y - 1)
      ans += (second[i] != '1');
    else
      ans += second[i] != '0';
  }
  cout << ans << "\n";
  return 0;
}
