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