#include <bits/stdc++.h>
using namespace std;
int N, M;
int h = 101;
void google() {
  int n, x, y, count = 0;
  cin >> n >> x >> y;
  string str;
  cin >> str;
  int j;
  for (int i = n - 1; i >= 0; i--) {
    j = (n - 1) - i;
    if (j == y && str[i] == '0')
      count++;
    else if (j < y && str[i] == '1')
      count++;
    else if (j > y && j < x && str[i] == '1')
      count++;
  }
  cout << count << "\n";
}
int solve() {
  int n;
  cin >> n;
  int a[n + 1];
  int count = 0;
  for (long long int i = 1; i < n + 1; i++) cin >> a[i];
  sort(a + 1, a + n + 1);
  int j = 1;
  for (long long int i = 1; i < n + 1; i++) {
    if (j <= a[i]) count++, j++;
  }
  cout << count << "\n";
}
void solve3() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int j;
  if (n % 2 == 0) {
    for (long long int i = 1; i < n - 1; i++) {
      j = i - 1;
      if (s[j] == s[j + 1] && j % 2 == 0) {
        if (s[j + 1] == s[j + 2])
          ;
      }
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t = 1;
  while (t--) {
    google();
  }
  return 0;
}
