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.
'''input
10
    


'''
from collections import defaultdict as df
from bisect import bisect_left as bl 
import sys
#maxn=1000001
n=input()
sq=int(n**0.5)+1
pf=n
for i in range(2,sq+1):
    if n%i==0:
        pf=i
        break

print n/pf

