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