How do I find the first two consecutive elements in my array of numbers?

Question

Using Ruby 2.4, I have an array of unique, ordered numbers, for example

[1, 7, 8, 12, 14, 15]

How do I find the first two elements whose differ

Answer 1

Simple example

   X = [1, 7, 8, 12, 14, 15]

   X.each_with_index do |item, index|
    if index < X.count - 1
     if (X[index+1]-X[index] == 1) 
      puts item
     end
   end
  end