81. merge sorted arrays

You are given a list of sorted non-descending integer arrays, write a function to merge them into one sorted non-descending array.

merge(
  [
    [1,1,1,100,1000,10000],
    [1,2,2,2,200,200,1000],
    [1000000,10000001],
    [2,3,3]
  ]
)
// [1,1,1,1,2,2,2,2,3,3,100,200,200,1000,1000,10000,1000000,10000001]

What is time complexity of your solution?