#include <bits/stdc++.h>
using ll = long long;
using ull = unsigned long long;
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  reverse(s.begin(), s.end());
  int ans = 0;
  for (int i = 0; i < y; i++) {
    if (s[i] == '1') ans++;
  }
  if (s[y] == '0') ans++;
  for (int i = y + 1; i < x; i++) {
    if (s[i] == '1') ans++;
  }
  cout << ans << endl;
  return 0;
}
