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 B {
    public static void main(String[] args) throws IOException {
        try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
            String firstLine = br.readLine();

            long startElement = Long.valueOf(firstLine);
            /*boolean[] sieve = getSieve((int) Math.sqrt(startElement) + 1);*/

            long count = 0;
            for (int i = 2; i < (int) Math.sqrt(startElement) + 1; i++) {
                if (startElement % i == 0) {
                    count = 1 + (startElement-i)/2;
                    break;
                }
            }

            if (count==0) {
                count = 1;
            }

            System.out.println(count);
        }
    }

    private static boolean[] getSieve(int n) {
        boolean[] isPrime = new boolean[n+1];
        for (int i = 2; i <= n; i++) {
            isPrime[i] = true;
        }

        for (int i = 2; i <= n; i++) {
            if (isPrime[i] == true) {
                for (int j = 2*i; j <= n; j+=i) {
                    isPrime[j] = false;
                }
            }
        }

        return isPrime;

    }
}
