A12227. Divisor Subtraction
编程题
普及/提高-
知识点
题目描述
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.
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.
输入格式
The only line contains a single integer $n$ ( $2 \le n \le 10^{10}$ ).
输出格式
Print a single integer — the number of subtractions the algorithm will make.
输入输出样例
输入 #1
5
输出 #1
1
输入 #2
4
输出 #2
2
说明/提示
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.
In the second example $2$ is the smallest prime divisor at both steps.