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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class B1076 {
	public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		long n = Long.parseLong(in.readLine());
		System.out.println(func(n, 0));
		
	}
	
	public static long func(long n, long c) {
		if(n == 0) {
			return c;
		}
		if(n % 2 == 0) {
			return func(n % 2, c + n/ 2);
		} else if(n% 3 == 0) {
			return func(n % 3, c+ n / 3);
		} else if(n% 5 == 0) {
			return func(n % 5, c + n / 5);
		} else if(n % 7 == 0) {
			return func(n % 7, c + n / 7);
		} else {
			boolean isPrime = false;
			for(int i = 2;i<=Math.floor(n);i++) {
				if(n % i == 0) {
					isPrime = true;
					break;
				}
			}
			if(isPrime) {
				return func(0, c+1);
			} else {
				return func(0, c+1);
			}
		}
		
	}
}
