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