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time limit per test: 0.25 sec.

memory limit per test: 4096 KB

memory limit per test: 4096 KB

input: standard

output: 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.

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).

Input

4

Output

0

Author: | Antony Popovich |

Resource: | Leningrad Regional School Programming Olympiad |

Date: | January 9, 2004 |

Codeforces (c) Copyright 2010-2019 Mike Mirzayanov

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