#include <bits/stdc++.h>
using namespace std;
int main() {
  int cnt = 0, n, x, y;
  string st;
  cin >> n >> x >> y;
  cin >> st;
  for (int i = n - 1; i > n - x - 1; i--) {
    if (st[i] == '1' && i != n - y - 1) cnt++;
    if (i == n - y - 1 && st[i] == '0') cnt++;
  }
  cout << cnt;
}
