#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 = n - 1; i >= (n - x); i--) {
    if (s[i] == '1' && i != n - y - 1) count++;
    if (s[i] == '0' && i == n - y - 1) count++;
  }
  cout << count;
}
