#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x, y;
  scanf("%d", &n);
  scanf("%d", &x);
  scanf("%d", &y);
  string s;
  cin >> s;
  int cnt = 0;
  reverse(s.begin(), s.end());
  for (int i = 0; i < y; i++) {
    if (s[i] != '0') cnt++;
  }
  if (s[y] != '1') cnt++;
  for (int i = y + 1; i < x; i++) {
    if (s[i] != '0') cnt++;
  }
  printf("%d\n", cnt);
  return 0;
}
