You are given an integer number n. The following algorithm is applied to it:

  1. if n = 0, then end algorithm; 
  2. find the smallest prime divisor d of n; 
  3. subtract d from n and go to step 1. 



Determine the number of subtrations the algorithm will make.

Input

The only line contains a single integer n (2 ≤ n ≤ 10^{10}).

Output

Print a single integer — the number of subtractions the algorithm will make.

Examples

Input


5


Output


1


Input


4


Output


2

Note

In the first example 5 is the smallest prime divisor, thus it gets subtracted right away to make a 0.

In the second example 2 is the smallest prime divisor at both steps.
import java.io.*;
import java.util.*;

public class Main {

    public static long smallestFactor(long x) {
        for (long i = 1; i * i <= x; i++) {
            if (x % i == 0) return i;
        }
        return x;
    }

    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        if (n % 2 == 0) {
            System.out.println(n / 2);
            return;
        }
        long fct = smallestFactor(n);
        int cnt = 1;
        n -= fct;
        System.out.println(n / 2+ 1);
    }

    static class Scanner {
        StringTokenizer st;
        BufferedReader br;
        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }
        public String next() throws IOException {
            while (st == null || !st.hasMoreTokens()) {
                st = new StringTokenizer(br.readLine());
            }
            return st.nextToken();
        }
        public int nextInt() throws IOException {
            return Integer.parseInt(next());
        }
        public long nextLong() throws IOException {
            return Long.parseLong(next());
        }
    }
}
