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())
if(n%2==0):
    print(n//2)
else:
    lp=n
    i=2
    while(i*i<=n):
        if(n%i==0):
            lp=i
            break
        i+=1
    print((n-lp)//2+1)


'''
////////////////      //////        ///////      //             ///////     //  //   //
////          //    ///   ///     ///    ///     //            ///  ///     ////     //
////    ////       ///     ///   ///      ///    //           /////////     ////     ///////
////     /////    ///       /// ///        ///   //          ///    ///     ////     //   //
//////////////     ///////////   ///////////     //////     ///     ///     //  //   //   //
'''

