#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  t = 1;
  while (t--) {
    int n;
    int x;
    int y;
    cin >> n >> x >> y;
    string s;
    cin >> s;
    int count = 0;
    for (int i = n - x; i < n; i++) {
      if (i == n - y - 1)
        count += (s[i] != '1');
      else
        count += (s[i] != '0');
    }
    cout << count;
  }
  return 0;
}
