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 DivSub{
	public static void main(String[] args) {
		try{
			BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
			long num = Long.parseLong(read.readLine());
			long ans = num;
			long count = 0;
		//	while(num>1){
				boolean flag = false;
				for(long i=2l;i<=Math.sqrt(num);i++){
					if(num%i==0){
						flag = true;
						ans = i;
						//num = num-i;
					//	count++;
						break;
					}
				}
				// if(!flag){
				// 	num -=num;
				// }
				count = num/ans ;
		//	}
			System.out.println(count);
		}catch(Exception e){

		}
	}
}