#!/usr/bin/env python
# from http://stackoverflow.com/a/19475021/
import heapq
 
def addtoheap(h, it):
    try:
        heapq.heappush(h, (next(it), it))
    except StopIteration:
        pass
 
def mergek(*lists):
    h = []
    for it in map(iter, lists):
        addtoheap(h, it)
    while h:
        min_, it = heapq.heappop(h)
        addtoheap(h, it)
        yield min_
 
for x in mergek([1, 3, 5], [2, 4, 6], [7, 8, 9], [10]):
    print(x)
 

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