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.
n = int(input())
i = 1
k = 0
if n % 2 == 0:
    print(n // 2)
else:
    while k != 1:
        if n % (4*i - 1) == 0:
            print(n // (4*i - 1))
            k = 1
        elif n % (4*i + 1) == 0:
            print(n // (4*i + 1))
            k = 1
        elif n == 4*i + 1 or n == 4*i - 1:
            print(1)
        i+=1
        
    
