#include <bits/stdc++.h>
using namespace std;
const long long mod = (1e+9) + 7;
const long long size = 2e5 + 9;
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long power(long long a, long long b, long long m = mod) {
  long long res = 1;
  while (b > 0) {
    if (b & 1) res = (res * a) % m;
    b = b >> 1;
    a = (a * a) % m;
  }
  return res;
}
void solve() {
  long long n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  long long cc = 0;
  reverse(s.begin(), s.end());
  long long ans = 0;
  for (long long i = 0; i < n; i++) {
    if (i + 1 > x) break;
    if (i + 1 <= y) {
      if (s[i] != '0') ans++;
    }
    if (i + 1 == y + 1) {
      if (s[i] != '1') ans++;
    }
    if (i + 1 > y + 1) {
      if (s[i] != '0') ans++;
    }
  }
  cout << ans << endl;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  clock_t beg = clock();
  solve();
  clock_t end = clock();
  fprintf(stderr, "%.3f sec, Copyright %c 2019 Skyscraper. \n",
          double(end - beg) / CLOCKS_PER_SEC, 184);
  return 0;
}
