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.
#!/usr/bin/env python3
import sys
import math

def rint():
    return map(int, sys.stdin.readline().split())
#lines = stdin.readlines()

n = int(input())

if n%2 == 0:
    cnt = n//2
else:
    for i in range(3, int(math.sqrt(n)+1)):
        if n % i == 0:
            cnt = 1 + (n-i)//2
            break
    else:
        cnt = 1

print(cnt)

