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 DivisorSubtraction
{
	public static void main(String args[])throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		PrintWriter pw = new PrintWriter(System.out);
		boolean ar[] = new boolean[100001];
		Arrays.fill(ar , true);
		ar[0] = ar[1] = false;

		for(int i = 2 ; i * i <= 100000 ; i++)
		{
			if(ar[i])
			{
				for(int j = i << 1 ; j <= 100000 ; j += i)
				{
					ar[j] = false;
				}
			}
		}
		LinkedList<Integer> list = new LinkedList<Integer>();
		for(int i = 0 ; i <= 100000 ; i++)
		{
			if(ar[i])
			{
				list.add(i);
			}
		}
		Collections.sort(list);
//		pw.println(list.size());



		
		long N = Long.parseLong(br.readLine().trim());

		long count = 0;	
/*		while(N > 0)
		{
			for(Integer t : list)
			{
				if((N % t) == 0)
				{
					if(t == 2)
					{
						count = count + (N / t);
						N = 0;
						break;
					}
					else
					{
						N -= t;
						count++;
						break;	
					}
				}
			}
		}*/
		for(Integer t : list)
		{
			if((N % t) == 0)
			{
				if(t == 2)
				{
					count = count + (N / t);
					break;
				}
				else
				{
					//System.out.println("Hello t==> " + t);
					N = N - t;
//					System.out.println("Hello N==> " + N);
					count++;
					if(N <= 0)
					{
						break;
					}
					else
					{
						count = count + (N / 2);
						break;
					}
				}
				
			}
		}
		if(count == 0)
		{
			pw.println("1");
		}
		else
		{
			pw.println(count);
		}
		pw.close();
	}
}
