#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse2")
void reverseStr(string& str) {
  int n = str.length();
  for (int i = 0; i < n / 2; i++) swap(str[i], str[n - i - 1]);
}
void printval(long long n, long long total) {
  if (total == n) {
    for (int i = 0; i < n; ++i) {
      cout << 1 << " ";
    }
  } else if (total == 1) {
    cout << n << " ";
  } else if (total <= n / 2 + 1) {
    printval(n / 2, total - 1);
    printval(n / 2, 1);
  } else {
    printval(n / 2, n / 2);
    printval(n / 2, total - n / 2);
  }
}
long long mint(long long a, long long b) {
  if (a > b)
    return b;
  else
    return a;
}
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  std::cout.precision(15);
  string s;
  long long n, x, y;
  cin >> n >> x >> y;
  cin >> s;
  reverseStr(s);
  long long count = 0;
  for (int i = 0; i < x; i++) {
    if (i == y) {
      if (s[i] == '0') count++;
    } else {
      if (s[i] == '1') count++;
    }
  }
  cout << count;
}
