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irb(main):001:0> def pairs_with_k_difference
irb(main):002:1>   require 'set'
irb(main):003:1>   n, k = $stdin.gets.match(/(\d+) (\d+)/).captures
irb(main):004:1>   if (n.is_a?Integer and k.is_a?Integer and n <= 10^5 and K>0 && K<1e9)
irb(main):005:2>     # n = n.to_i
irb(main):006:2*     # k = k.to_i
irb(main):007:2*     flag = 0
irb(main):008:2>     numbers = Set.new($stdin.gets.split)
irb(main):009:2>     numbers.each do|a|
irb(main):010:3*       if !a.is_a? Integer
irb(main):011:4>       flag = flag + 1
irb(main):012:4>       end
irb(main):013:3>     end
irb(main):014:2>     if flag == 0
irb(main):015:3>       puts numbers.count { |num| numbers.include?(num-k) }
irb(main):016:3>     else
irb(main):017:3*       $stdin.puts "Please enter numbers"
irb(main):018:3>     end
irb(main):019:2>   else
irb(main):020:2*     $stdout.puts "Please enter values within limits"
irb(main):021:2>   end
irb(main):022:1> end
=> nil
irb(main):023:0> pairs_with_k_difference
5 2
Please enter values within limits
=> nil
irb(main):024:0>