#include <bits/stdc++.h>
using namespace std;
template <class A, class B>
ostream &operator<<(ostream &out, const pair<A, B> &a) {
  return out << "(" << a.first << "," << a.second << ")";
}
template <class A>
ostream &operator<<(ostream &out, const vector<A> &a) {
  for (const A &it : a) out << it << " ";
  return out;
}
template <class A, class B>
istream &operator>>(istream &in, pair<A, B> &a) {
  return in >> a.first >> a.second;
}
template <class A>
istream &operator>>(istream &in, vector<A> &a) {
  for (A &i : a) in >> i;
  return in;
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  reverse((s).begin(), (s).end());
  long long cnt = 0;
  for (long long i = 0; i < x; i++) {
    if ((i == x || i == y)) {
      cnt += s[i] == '0';
    } else
      cnt += s[i] == '1';
  }
  cout << cnt;
}
