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.
pr=[1]*100001
pr[0],pr[1]=0,0
primes=[]
for i in range(2,100001):
    if(pr[i]==1):
        primes.append(i)
        for j in range(i*i,100001,i):
            pr[j]=0
def prime(n):
    for i in range(2,int(n**0.5)+2):
        if(n%i==0):
            return False
    return True
def dope(n):
    if(prime(n)):
        return 1
    for i in primes:
        if n%i==0:
            return n//i
print(dope(int(input())))
    