#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x, y, ans = 0;
  string s;
  cin >> n >> x >> y;
  cin >> s;
  reverse(s.begin(), s.end());
  for (int i = 0; i < s.length(); i++) {
    if (i < y) {
      if (s[i] != '0') ans += 1;
    } else if (i == y) {
      if (s[i] != '1') ans += 1;
    } else if (i > y && i < x) {
      if (s[i] != '0') ans += 1;
    } else
      break;
  }
  cout << ans;
  return 0;
}
