#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int main() {
  int n, x, y, ans = 0;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  for (int i = n - x; i < n; i++) {
    if (i == n - 1 - y) {
      if (s[i] != '1') ans++;
    } else {
      if (s[i] != '0') ans++;
    }
  }
  cout << ans;
  return 0;
}
