#include <bits/stdc++.h>
using namespace std;
char c1[250001], c2[250001];
int n, x, y, i, ans;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cin >> n >> x >> y;
  for (i = 1; i <= n; i++) {
    cin >> c1[i];
    c2[i] = '0';
  }
  c2[n - y] = '1';
  for (i = n - x + 1; i <= n; i++)
    if (c1[i] != c2[i]) ans++;
  cout << ans << '\n';
  return 0;
}
