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.
var nn = +readline();

function solve(n) {
    if (n % 2 === 0) {
        return n / 2;
    }
    
    var square = Math.sqrt(n);
    var d = 3;
    var smallestDivisor = n;
    while (d < square) {
        if (n % d === 0) {
            smallestDivisor = d;
            break;
        }
        d += 2;
    }

    return n / smallestDivisor;
}

write(solve(nn));