#include <bits/stdc++.h>
int main() {
  std::ios_base::sync_with_stdio(false);
  long n, x, y;
  std::cin >> n >> x >> y;
  char c;
  while (n > x) {
    --n;
    std::cin >> c;
  }
  long ans = 0;
  while (n > 0) {
    --n;
    std::cin >> c;
    if ((y < n && c != '0') || (y == n && c == '0') || (y > n && c != '0'))
      ++ans;
  }
  std::cout << ans << std::endl;
}
