I am getting a TLE on this [problem](http://mirror.codeforces.com/contest/404/problem/C) using DFS. This is my [submission](http://mirror.codeforces.com/contest/404/submission/30168369). Can someone suggest some optimizations?
| # | User | Rating |
|---|---|---|
| 1 | Benq | 3792 |
| 2 | VivaciousAubergine | 3647 |
| 3 | Kevin114514 | 3603 |
| 4 | jiangly | 3583 |
| 5 | strapple | 3515 |
| 6 | tourist | 3470 |
| 7 | dXqwq | 3436 |
| 8 | Radewoosh | 3415 |
| 9 | Otomachi_Una | 3413 |
| 10 | Um_nik | 3376 |
| # | User | Contrib. |
|---|---|---|
| 1 | Qingyu | 158 |
| 2 | adamant | 152 |
| 3 | Proof_by_QED | 146 |
| 3 | Um_nik | 146 |
| 5 | Dominater069 | 144 |
| 6 | errorgorn | 141 |
| 7 | cry | 139 |
| 8 | YuukiS | 135 |
| 9 | chromate00 | 134 |
| 9 | TheScrasse | 134 |
