231. Prime Sum
time limit per test: 0.25
memory limit per test: 4096
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.
The input of the problem consists of the only integer N (1<=N<=10^6).
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).
|Resource:||Leningrad Regional School Programming Olympiad
|Date:||January 9, 2004
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