#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9 + 1000;
const long long INF64 = 1e18 + 1000;
const int N = 6 * 100 * 1000 + 100;
const int MOD = 1e9 + 7;
long long gcd(long long a, long long b) { return a == 0 ? b : gcd(b % a, a); }
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  int ans = 0;
  for (int i = int(n - x); i < int(n); ++i) {
    if (i == (n - y - 1) && s[i] == '0')
      ans++;
    else if (s[i] == '1' && i != (n - y - 1))
      ans++;
  }
  cout << ans;
}
