#include <bits/stdc++.h>
using namespace std;
long long t, n, x, y, m, k, a[100005], b[100005];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> n >> x >> y;
  string s;
  cin >> s;
  int ans = 0;
  int cnt = 1;
  for (int i = n - 1; cnt <= x; i--, cnt++) {
    if (cnt == y + 1) {
      if (s[i] == '0') ans++;
    } else if (s[i] == '1')
      ans++;
  }
  cout << ans;
  return 0;
}
