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.
# TAIWAN NUMBER ONE!!!!!!!!!!!!!!!!!!!
# TAIWAN NUMBER ONE!!!!!!!!!!!!!!!!!!!
# TAIWAN NUMBER ONE!!!!!!!!!!!!!!!!!!!
from sys import stdin, stdout
from itertools import accumulate

N = int(input())
#s = input()
#N,M,K,Q = [int(x) for x in stdin.readline().split()]
#arr = [int(x) for x in stdin.readline().split()]

if N%2==0:
    print(N//2)
    quit()
    
found_prime = 0
for i in range(2,100001):
    if i*i>N:
        break
    else:
        if N%i==0:
            found_prime = i
            break

if found_prime==0:
    print(1)
else:
    N -= found_prime
    print(1+N//2)
            