a = [2, 4, 2, 23, 26, 5456, 565, 12, 347]

# 1
a = a.sort
puts a.inspect

# 2
puts a.max
puts a.min
puts a.minmax.inspect

# 4
puts a.uniq.inspect

# 3
(0..a.length - 1).step(2).each do |index|
  a[index] = a[index] * (-1)
end

puts a.inspect

b = []

(0..a.length - 1).step(2).each do |index|
  b[index/2] = a[index]
end

puts b.inspect