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 a{
public static void main(String[]args)throws Exception{
  //  File f=new File("/home/ujjwal/Desktop/hi.txt");
Scanner sc=new Scanner(System.in);
long l=sc.nextLong(),d=0,c=0;//5

d=primediv(l);//3 
if(d%2==1){
l=l-d;c++;
}
c=(l/2)+c;
if(d==-1)
c=1;

System.out.println(c);
}
public static long primediv(long n){
for(long i=2;i<=100;i++){
if(n%i==0 && (prime(i)==true)){
return i;
}
}
return -1;
}
public static boolean prime(long a){
int c=0;
for(int i=2;i<=a/2;i++){
if(a%i==0)
return false;
}
return true;
}


}
