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