#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, x, y;
  scanf("%lld", &n);
  scanf("%lld", &x);
  scanf("%lld", &y);
  string str, temp;
  cin >> str;
  temp = str;
  long long int i = n - 1;
  while (x--) {
    temp[i] = '0';
    i--;
  }
  i = n - 1;
  while (y--) {
    temp[i] = '0';
    i--;
  }
  temp[i] = '1';
  long long int ans = 0;
  for (long long int i = 0; i < n; i++) ans += (str[i] != temp[i]);
  printf("%lld\n", ans);
  return 0;
}
