#include <bits/stdc++.h>
using namespace std;
void input() {}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  input();
  long long int n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  long long int idx = n - 1 - y;
  long long int cnt = 0;
  for (long long int i = n - x; i < n; i++) {
    if (i == idx) {
      if (s[i] == '0') cnt++;
      continue;
    }
    if (s[i] == '1') cnt++;
  }
  cout << cnt;
  return 0;
}
