Description:
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 Format:
The only line contains a single integer $$$n$$$ ($$$2 \le n \le 10^{10}$$$).
Output Format:
Print a single integer — the number of subtractions the algorithm will make.
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.