Check if the number is Sophie Germain prime, prime number, or not

b-sophie-germain.rb

#See also: ABC084 D - 2017-like Number

require "set"

n = gets.to_i

require "prime"

n_is_prime= false
n21_is_prime = false
Prime.each(n*2+1) { |prime| # これはひどい
  n_is_prime = true if prime == n
  n21_is_prime = true if prime == n*2+1
}

if n_is_prime
  if n21_is_prime
    puts "Sophie Germain"
  else
    puts "Prime"
  end
else
  puts "Composite"
end