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.
import math

def sieve(n):
    """Sieve away and only primes are left."""
    primes = set(range(2, n+1))
    # print(len(primes))
    for i in range(2,int(n**0.5+1)):
        if i in primes:
            primes -= set(range(i*i, n+1, i))
    return primes

n = input()
n = int(n)
prime = sieve(100000)
# print(prime)
ans = 1
for p in prime:
    if n%p == 0:
        ans = n // p
        break
print(ans)
