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