#include <bits/stdc++.h>
using namespace std;
int main() {
  long int n, x, y, i, r, c = 0;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  if (s[n - y - 1] - 48 != 1) {
    c++;
  }
  for (i = n - 1; i >= n - x; i--) {
    if (i == n - y - 1) {
      continue;
    }
    if (s[i] - 48 != 0) c++;
  }
  cout << c;
  return 0;
}
