#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  long long ans = 0, a = 0, b = 0;
  reverse(s.begin(), s.end());
  cerr << s << endl;
  for (long long i = 0; i < y; i++) {
    if (s[i] == '1') {
      ans++;
    }
  }
  cerr << ans;
  if (s[y] == '0') ans++;
  for (long long i = y + 1; i < x; i++) {
    if (s[i] == '1') ans++;
  }
  cout << ans;
}
int main() {
  solve();
  return 0;
}
