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.
int_inp   = lambda: int(input()) #integer input
strng     = lambda: input().strip() #string input
strl      = lambda: list(input().strip())#list of strings as input
mul       = lambda: map(int,input().split())#multiple integers as inpnut
mulf      = lambda: map(float,input().split())#multiple floats as ipnut
seq       = lambda: list(map(int,input().split()))#list of integers
import math
from collections import Counter,defaultdict

n = input()
n = int(n)
ans = 0
for i in range (2,1000001):
    if (n%i == 0):
        print(1 + (n - i) // 2)
        exit()
print(1)
