[[1,2],[3,4],[5,6],[7,8],[9,9],[0,1],[2,3]]

 mas = [[1, 2], [3, 4], [5, 6], [7, 8], [9, 9], [0, 1], [2, 3]]
count = 5
tmp = []
for i in mas:
    tmp.extend(i)
print(tmp[:count])