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())
kt = n
cnt =0
while (True):
    if (n%2==0):
        cnt+=n//2
        break
    elif (n%3==0):
        cnt+=n//3
        n//=3
    elif (n%5==0):
        cnt+=n//5
        n//=5
    elif (n%7==0):
        cnt+=n//7
        n//=7
    else:
        if (kt==n):
            print(1)
            exit(0)
        elif (n==1):
            break
        else:
            cnt+=1
            break
print(cnt)
