<|im_start|>system
Please reason step by step, and put your final answer within \boxed{}.<|im_end|>
<|im_start|>user
Given the following crystal representation:
10.9 10.9 10.9
15 15 15
Na
0.00 0.00 0.99
Na
0.00 0.00 0.45
Nb
0.00 0.00 0.59
Si
0.00 0.00 0.90
Identify the crystal system.<|im_end|>
<|im_start|>assistant
Given the following crystal representation:
10.9 10.9 10.9
15 15 15
Na
0.00 0.00 0.99
Na
0.00 0.00 0.45
Nb
0.00 0.00 0.59
Si
0.00 0.00 0.90
Identify the crystal system.