#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using dd = double;
const int N = (int)1e6 + 7;
int a[N];
vector<int> foo;
void help() {}
void TaoCode() {
  int n, x, y;
  cin >> n >> x >> y;
  string bit;
  cin >> bit;
  int cnt = 0;
  for (int i = (0); i < (x); i++) {
    if (i == y and bit[(int)bit.size() - i - 1] == '0') {
      cnt++;
    } else if (i != y and bit[(int)bit.size() - i - 1] == '1') {
      cnt++;
    }
  }
  cout << cnt;
}
int main() {
  ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  TaoCode();
  return 0;
}
