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