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.
from math import *
n=int(input())
ans=0
g=int(sqrt(n)//1)+1
l=[0]*g
l[0]=1
l[1]=1
d=[]
for i in range(2,g):
    if l[i]==0:
        for j in range(i+i,g,i):
            l[j]=1
        d.append(i)
k=0

while n and k<len(d):
    if n%d[k]==0:
        ans=n//d[k]
        n=0
    else:
        k+=1
if ans==0:
    ans=1
print(ans)
