Code golf: combining multiple sorted lists into a single sorted list

Question

Implement an algorithm to merge an arbitrary number of sorted lists into one sorted list. The aim is to create the smallest working programme, in whatever language you like.

Answer 1

resubmitted

Python - 74 chars (counting whitespace and newlines)

def m(i):
 y=[];x=sum(i,[])
 while x:n=min(x);y+=[n];x.remove(n)
 return y

i is input as list of lists

Usage:

>>> m([[1,5],[6,3]])
[1, 3, 5, 6]

Answer 2

Haskell like (158, but more than 24 spaces could be removed.):

mm = foldl1 m where
  m [] b = b
  m a [] = a
  m (a:as) (b:bs)
   | a <= b = a : m as (b:bs)
   | true   = b : m (a:as) bs