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

public class Main
{
	public static void main(String[] args)
	{
		FastReader reader = new FastReader();
		PrintWriter writer = new PrintWriter(System.out);

		long n = reader.nextLong();
		int root = 0;

		int[] prime = new int[100001];

		for (int i=2; i<100001; i++)
			prime[i] = i;

		for (int i=2; i<100001; i++)
			if (prime[i] == i)
				for (int j=2*i; j<100001; j+=i)
					prime[j] = Math.min(prime[j], i);

		for (int i=2; i<100001; i++)
			if (n%i == 0)
			{
				root = i;
				break;
			}



		if (root > 0)
		{
			int count = 0;

			if (n%2 == 1)
			{
				count++;
				n -= root;
			}

			count += n/2;

			writer.print(count);
		}
		else
			writer.print(1);

		writer.close();
	}

	static class FastReader
	{
		BufferedReader br;
		StringTokenizer st;

		public FastReader()
		{
			br = new BufferedReader(new InputStreamReader(System.in));
		}

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

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

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

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

		String nextLine()
		{
			String str = "";
			try
			{
				str = br.readLine();
			}
			catch (IOException e)
			{
				e.printStackTrace();
			}
			return str;
		}
	}
}