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 B
{

	static ArrayList<Integer> primes;
	static int[] isComposite;

	static void sieve(int N) {
		isComposite = new int[N + 1];
		isComposite[0] = isComposite[1] = 1;
		primes = new ArrayList<Integer>();

		for (int i = 2; i <= N; ++i)
			if (isComposite[i] == 0) {
				primes.add(i);
				if (1l * i * i <= N)
					for (int j = i * i; j <= N; j += i)
						isComposite[j] = 1;
			}
	}
	
	
	static boolean isPrime(long N) {
		if (N < isComposite.length)
			return isComposite[(int)N] == 0;
		for (int p : primes) // may stop if p * p > N
			if (N % p == 0)
				return false;
		return true;
	}


	static long f(long x)
	{
		if(x == 0)
			return 0 ; 
		
		long div = Long.MAX_VALUE ; 
				
		for(long i = 1 ; i * i <= x ; i++)
			if(x % i == 0)
			{
				div = Math.min(div, Math.min(!isPrime(i) ? Long.MAX_VALUE : i, !isPrime(x / i) ? Long.MAX_VALUE : x / i));
				
			}
		
		return  (x / div) + f(x % div); 
		
		
		
	}
	public static void main(String[] args) throws Exception
	{
		Scanner sc = new Scanner(System.in);
		PrintWriter out  = new PrintWriter(System.out);
		sieve((int)1e7);
		
		long x = sc.nextLong();
		
		out.println(f(x));
		
		
		
		
		out.flush();
		out.close();
		
		

	}
	static class Scanner 
	{
		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}
		
		public Scanner(String path) throws Exception{	br = new BufferedReader(new FileReader(path));}

		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());}


		public double nextDouble() throws IOException {return Double.parseDouble(next());}

	}

	static void shuffle(int[] a)
	{
		int n = a.length;
		for(int i = 0; i < n; i++)
		{
			int r = i + (int)(Math.random() * (n - i));
			int tmp = a[i];
			a[i] = a[r];
			a[r] = tmp;
		}
	}



}
