Optimize problem 10 solution

```
Timing problem 10. Running timer 3 time(s).
Run 001 0:00:05.519310
Run 002 0:00:05.537555
Run 003 0:00:05.546229

======== Stats ========
Slowest: 0:00:05.546229
Fastest: 0:00:05.519310
Average: 0:00:05.534365
```