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