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())

def func(n):
	if(n%2==0):
		return (n//2)
	index=2
	check=False
	while(index*index<=n):
		if(n%index==0):
			check=True
			return 1+func(n-index)
		index+=1
	if(check==False):
		return 1

print(func(n))


	