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.
def prime_factors(n):
    i = 2
    f = []
    while i * i <= n:
        if n % i:
            i += 1
        else:
            n //= i
            f.append(i)
    if n > 1:
        f.append(n)
    return f


def solve(n):
    ans = 0
    f = prime_factors(n)
    fs = set(f)
    for i in fs:
        ans += 2 ** (f.count(i) - 1)
    return ans


def main():
    n = int(input())
    print(solve(n))


main()
