#include <bits/stdc++.h>
using namespace std;
void start() {}
void sober() {
  long long int n, x, y;
  cin >> n >> y >> x;
  string s;
  cin >> s;
  long long int count = 0;
  for (int i = n - 1; i != n - y - 1; i--) {
    if (i == n - 1 - x) {
      if (s[i] == '0') count++;
    } else if (s[i] == '1') {
      count++;
    }
  }
  cout << count << "\n";
}
int main() {
  start();
  int t = 1;
  while (t--) sober();
}
