Problem1032--Handle intervals

1032: Handle intervals

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Time Limit : 1.000 sec  Memory Limit : 128 MiB

Description

There is a set of N intervals, some of them might be overlapping each other, in this problem, please merge the overlapping intervals.





Input

the first line has one integer which is N
In the following N lines, each line has two integer X1 and X2 which stand for the interval [X1, X2]  (X1 <X2]
1 <= N <= 1,000,000   ,   1 <= Xi <= 100,000,000

Output

the intervals which do not have overlapping in ascending order

Sample Input Copy

7
1 5
8 20
3 6
9 10
50 100
19 25
25 27

Sample Output Copy

1 6
8 27
50 100

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