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