#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x, y;
  string s;
  cin >> n >> x >> y;
  getline(cin >> ws, s);
  int cnt = 0;
  for (int i = 0; i < x; i++)
    if (i != y && s[n - 1 - i] == '1')
      cnt++;
    else if (i == y && s[n - 1 - i] == '0')
      cnt++;
  cout << cnt << "\n";
  return 0;
}
