#include <bits/stdc++.h>
using namespace std;
int main() {
  int t = 1;
  while (t--) {
    int n, x, y;
    cin >> n >> x >> y;
    string nn;
    cin >> nn;
    int ans = 0;
    for (int i = n - x; i < n; ++i) {
      if (i == n - y - 1)
        ans += nn[i] != '1';
      else
        ans += nn[i] != '0';
    }
    cout << ans << endl;
  }
}
