#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, m, l;
  cin >> n >> l >> m;
  string s;
  cin >> s;
  long long ans = 0;
  if (s[n - m - 1] == '0') ans++;
  for (long long i = n - m; i < n; i++) {
    if (s[i] == '1') ans++;
  }
  long long x = n - m - 1;
  for (long long i = n - l; i < x; i++) {
    if (s[i] == '1') ans++;
  }
  cout << ans << endl;
  return 0;
  ;
}
