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 {
    private void solve() {
        long n = nextLong();
        if(n%2==0)out.print(n/2);
        else if(isPrime(n))out.print(1);
            else{
            long k = 1;
            do{
                k+=2;
            }while(n%k!=0);
            n-=k;
            out.print(1+(n/2));
        }
    }

    private boolean isPrime(long n) {
        for (long i = 2; i < Math.sqrt(n); i++) {
            if(n%i==0)return false;
        }
        return true;
    }


    public static void main(String[] args) {
        new Main().run();
    }

    BufferedReader br;
    StringTokenizer st;
    PrintWriter out;

    private void run() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
            out = new PrintWriter(System.out);
//            br = new BufferedReader(new FileReader("input.txt"));
//            out = new PrintWriter(new FileWriter("output.txt"));
            solve();
            br.close();
            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private long nextLong() {return Long.parseLong(next()); }

    private int nextInt() {
        return Integer.parseInt(next());
    }

    private String next() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
                return "END_OF_FILE";
            }
        }
        return st.nextToken();
    }
}