#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7, N = 1e5 + 5;
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n, x, y;
  cin >> n >> x >> y;
  string num;
  cin >> num;
  reverse(num.begin(), num.end());
  int ans = 0, i = 0;
  while (i < y) {
    if (num[i] != '0') ans++;
    i++;
  }
  if (num[i] != '1') ans++;
  i++;
  while (i < x) {
    if (num[i] != '0') ans++;
    i++;
  }
  cout << ans << "\n";
  return 0;
}
