CF1076B.Divisor Subtraction

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.

The only line contains a single integer $n$ ( $2 \le n \le 10^{10}$ ).

Print a single integer — the number of subtractions the algorithm will make.

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.