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 math
n = int(input())

resposta = 0

if(n % 2 == 0):
    resposta = n//2
else:
    ok = False
    menor = 0
    for i in range(2,int(math.sqrt(n)) +1):
        if(n % i == 0):
            menor = i
            ok = True
            break
        
    k =(n - menor) // 2
    
    if(ok):
        resposta = k + 1
    else:
        resposta = 1

print(resposta)
 			   	  	 	 		 										 		