231. Prime Sum
time limit per test: 0.25
sec.
memory limit per test: 4096
KB
input: standard
output: standard
Find all pairs of prime numbers (A, B) such that A<=B and their sum is also a prime number and does not exceed N.
Input
The input of the problem consists of the only integer N (1<=N<=10^6).
Output
On the first line of the output file write the number of pairs meeting the requirements. Then output all pairs one per line (two primes separated by a space).
Sample test(s)
Input
4
Output
0
Author:  Antony Popovich

Resource:  Leningrad Regional School Programming Olympiad

Date:  January 9, 2004

Server time: 20160531 20:59:00  Online Contester Team © 2002  2016. All rights reserved. 

