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