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.
def isPrime(n):
    for i in range(2,int(n**0.5)+1):
        if n%i == 0:
            return False
    return True

pr = []
def sieve():
    n = 10**5+1
    prime = [True for i in range(n+1)] 
    p = 2
    while (p * p <= n): 
        if (prime[p] == True): 
            for i in range(p * 2, n+1, p): 
                prime[i] = False
        p += 1
    for i in range(2,n+1):
        if prime[i] == True:
            pr.append(i)
        
n = int(input())

if isPrime(n):
    print(1)
else:
    sieve()
    ans = 0

    for i in pr:
        if n%i is 0:
            while n!=0 and n%i == 0:
                k = n//i
                n -= k*i
                ans += k

            if n is 0:
                break
    print(ans)
