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())
d = -1

def isPrime(x):
    div = 0
    for i in range(2, x):
        if x % i == 0:
            div += 1
            break
    if div == 0:
        return True
    else:
        return False

for i in range(2, n+1):
    if n % i == 0 and isPrime(i) == True:
        d = i
        break
if d == -1:
    print (1)
else:
    print (int(n/d))
 	  		   		   	 			 			