#include <bits/stdc++.h>
using namespace std;
char s[200005];
int main() {
  int n, x, y, ans = 0;
  scanf("%d%d%d", &n, &x, &y);
  scanf("%s", s + 1);
  for (int i = n; i >= n - y + 1; i--) {
    if (s[i] == '1') ans++;
  }
  if (s[n - y] == '0') ans++;
  for (int i = n - y - 1; i >= n - x + 1; i--) {
    if (s[i] == '1') ans++;
  }
  cout << ans << "\n";
}
