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