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.
n = int(input())
flag = 0
ans = 0

if (n % 2 == 0):
    ans = n / 2
    flag = 1
elif (n == 1):
	ans = 1
elif (n % 2 == 1):
    for d in range(2, int(n ** 0.5) + 1):
        if (n % d == 0):
            ans = 1 + (n - d) / 2
            flag = 1
            break
if (flag == 0):
    ans = 1; 
print(int(ans))