同和创作矩阵 › ›博文归档› 技术博文归档 › 查看内容

22869_Goldbach'sConjecture

2022-5-16 18:23| 发布者: Hocassian| 查看: 21| 评论: 0|原作者: 肇庆学院ACM合集

摘要:

C:\Users\Administrator\Downloads\2019-10-12-10-14-5-8950733803899-Problem List-采集的数据-后羿采集器.html

Pro.ID

22869

Title

Goldbach's Conjecture

Title链接

http://10.20.2.8/oj/exercise/problem?problem_id=22869

AC

Submit

Ratio

0.00%

时间&空间限制

Time Limit: 0/0 MS (Java/Others) Memory Limit: 0/0 K (Java/Others)

描述

For any even number n greater than or equal to 4, there exists at least one pair of prime numbers p₁ and p₂ such that

n=p₁+p₂

This conjecture has not been proved nor refused yet. No one is sure whether this conjecture actually holds. However, one can find such a pair of prime numbers, if any, for a given even number. The problem here is to write a program that reports the number of all the pairs of prime numbers satisfying the condition in the conjecture for a given even number.

A sequence of even numbers is given as input. There can be many such numbers. Corresponding to each number, the program should output the number of pairs mentioned above. Notice that we are interested in the number of essentially different pairs and therefore you should not count (p₁, p₂) and (p₂, p₁) separately as two different pairs.

输入

An integer is given in each input line. You may assume that each integer is even, and is greater than or equal to 4 and less than 2¹⁵. The end of the input is indicated by a number 0.

输出

Description

For any even number n greater than or equal to 4, there exists at least one pair of prime numbers p₁ and p₂ such that

n=p₁+p₂

Input

An integer is given in each input line. You may assume that each integer is even, and is greater than or equal to 4 and less than 2¹⁵. The end of the input is indicated by a number 0.

Output

Each output line should contain an integer number. No other characters should appear in the output.

Sample Input

6
10
12
0

Sample Output

1
2
1

Hint

请忽略本题

Source

Norgesmesterskapet 2002