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.
x = eval(input())
i=2
sum = 0
flag = True
if x%2==0:
  print(int(x/2))
  
else:
  while i<=(x**(1/2)):
    if x%i==0:
      sum=int(((x-i)/2)+1)
      flag = False
      break
    else :
      i+=1
  if flag:
    print(1)
  else:
    print(sum)

