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