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 smallestDivisor(n):
    if (n % 2 == 0):
        return 2;
    i = 3;
    while(i * i <= n):
        if (n % i == 0):
            return i;
        i += 2;
 
    return n;
n=int(input())
s=0
d=smallestDivisor(n)
s=n//d
print(s)
