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())
ans=0
while(n>0):
	if not n&1:
		ans+=(n//2)
		n=0
	elif n%2==0 or n%5==0 or n%3==0 or n%7==0 or n%11==0:
		if n%2==0:
			n-=2
			ans+=1
		elif n%3==0:
			ans+=1
			n-=3
		elif n%5==0:
			ans+=1
			n-=5
		elif n%7==0:
			ans+=1
			n-=7
		elif n%11==0:
			ans+=1
			n-=11
	else:
		ans+=1
		n=0
print(ans)