#include <bits/stdc++.h>
using namespace std;
long long powermodm(long long x, long long n, long long M) {
  long long result = 1;
  while (n > 0) {
    if (n % 2 == 1) result = (result * x) % M;
    x = (x * x) % M;
    n = n / 2;
  }
  return result;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  long long moves = 0;
  long long i = n - 1, j = 0;
  while (j < x) {
    if (s[i] == '1' && i != n - y - 1) {
      moves++;
    }
    j++;
    i--;
  }
  if (s[n - y - 1] == '0') {
    moves++;
  }
  cout << moves << '\n';
  return 0;
}
