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