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())
l=[0]*(100001)
l[0]=-1;
l[1]=-1;

t=[];
flag=0;
for i in range(2,(100001)//2):
    if(l[i]!=-1):

        for j in range((2*i),(100001),i):
            l[j]=-1;

for i in range(2,(100001)):
    if l[i]!=-1:
        t.append(i)
#print(t)
for _ in t:
    if n%_==0:
        n-=_
        #print('divided')
        flag=1
        break;

if flag==0:
    print(1)
else:
    print((n//2)+1)


