#include <bits/stdc++.h>
using namespace std;
void displayCtr() {}
int main() {
  int t = 1;
  while (t--) {
    int n, first, second;
    cin >> n >> first >> second;
    string key;
    cin >> key;
    vector<int> form;
    int cnt = 0;
    for (int i = n - 1; i >= n - first; i -= 1) {
      if (i == n - second - 1) {
        if (key[i] == '0') cnt++;
      } else if (key[i] == '1') {
        cnt++;
      }
    }
    cout << cnt << "\n";
  }
}
