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.
# @author Nayara Souza
# UFCG - Universidade Federal de Campina Grande
# AA - Basico

n = int(input())
count = 0
i = 2

if n % 2 == 0:
    print(n//2)

else:
    x = 0
    while i * i <= n:
        if n % i == 0:
            x = ((n - i) // 2) + 1
            break
        i += 1
    if x == 0:
        print(1)
    else:
        print(x)
 					 	  	 	    		  	 	 					