> 
> to solve this problem, I used Indexed tree recorded sorted sequences.
> 
> for example)
> 
> level 0) [1,  2,  3,  4,  5,  6,  7,  inf]
> level 1) [1,  2,  5,  6] [3,  4,  7,  inf]
> level 2) [1,  5] [2,  6] [3,  7] [4,  inf]
> level 3) [1] [5] [2] [6] [3] [7] [4] [inf]
> 
> [...] stand for a node of indexed tree.
> 
> it works, but not enough. therefore, i got TLE.
> 
> how can i reduce execution time?

Your algorithm is OK, use Merge Sort to to sort sequences between levels.