#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x, y;
  cin >> n >> x >> y;
  string num;
  cin >> num;
  num = num.substr(num.length() - x, x);
  cout << count(num.begin(), num.end() - y - 1, '1') +
              count(num.end() - y, num.end(), '1') +
              (*(num.end() - y - 1) == '1' ? 0 : 1);
  return 0;
}
