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/python3
from collections import Counter

def readint():
    return int(input())


def readline():
    return [int(c) for c in input().split()]


def divisors(n):
    i = 2
    res = Counter()
    while i * i <= n:
        if n % i == 0:
            while n % i == 0:
                n //= i
                res[i] += 1
        i += 1
    if n != 1:
        res[n] = 1

    return res
            


def main():
    n = int(input())
    d = divisors(n)
    _min = min(d.keys())
    prod = 1
    for k, v in d.items():
        if k == _min and v > 1:
            prod *= k * (v - 1)
        elif k != _min:
            prod *= k * v
            
    print(prod)
        


if __name__ == '__main__':
    main()
