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.
from collections import deque
from math import sqrt,ceil
def ii(): return int(input())
def si(): return input()
def mi(): return map(int,input().strip().split(" "))
def li(): return list(mi())
def isprime(n):
    if(n==1):
        return 0
    for i in range(2,int(sqrt(n))+1):
        if(n%i==0):
            return 0
    return 1
n=ii()
if(isprime(n)):
    print('1')
elif(n%2==0):
    print(n//2)
else:
    c=0
    a=[]
    b=[]
    for i in range(2,int(sqrt(n))+1):
        if(n%i==0 and isprime(i)):
            a.append(i)
        if(i!=n//i and isprime(n//i)):
            b.append(n//i)
    if(len(a)!=0):
        x=min(a)
    else:
        x=min(b)
    n-=x
    print(n//2+1)
                    
        
        