#include <bits/stdc++.h>
using namespace std;
const int MOD = 1000000007;
const double PI = 4 * atan(1);
const int MX = 100000;
int t[300005];
int main() {
  int y, x, n;
  cin >> n >> y >> x;
  string second;
  cin >> second;
  int res = 0;
  for (int i = n - y; i < n; i++) {
    if (i == n - x - 1)
      res += (second[i] == '0');
    else
      res += (second[i] == '1');
  }
  cout << res;
}
