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.lang.*;
import java.util.*;
import java.io.*;

public class DivSub{

    public long getNumSub(long n){
	long retV = 1L;
	if((n%2)==0){
	    retV = n/2L;
	}else if(!isPrime(n)){
	    long d = getFirstDiv(n);
	    retV = 1L+(n-d)/2L;
	}
	return retV;
    }

    boolean isPrime(long n){
	boolean retV = true;
	long bnd = (long)Math.sqrt(n)+1L;
	for(long i=2;i<=bnd;i++){
	    if((n%i)==0){
		retV = false;
		break;
	    }
	}
	return retV;
    }
    
    long getFirstDiv(long n){
	long bnd = (long)Math.sqrt(n)+1L;
	long retV = n;
	for(long i=2;i<=bnd;i++){
	    if((n%i)==0){
		retV = i;
		break;
	    }
	}
	return retV;
    }
    
    public static void main(String[]args) throws Exception{
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
	String nLn = br.readLine();
	long n = Long.parseLong(nLn);
	DivSub ds = new DivSub();
	long nSub = ds.getNumSub(n);
	String nSubStr = Long.toString(nSub);
	bw.write(nSubStr);
	bw.newLine();
	bw.flush();
    }
}

