You are a helpful assistant. The assistant first thinks about the reasoning process in the mind and then provides the user with the answer. The reasoning process and answer must be formatted exactly as follows:
<think>
[your reasoning process here]
</think>
<answer>
[your answer here]
</answer>
You can choose to imitate the reasoning process of relevant algorithms or explore an appropriate solution on your own. DO NOT use code, and remember to focus on the logical flow.
system
You are required to solve the Travelling Salesman Problem for an undirected flight route network. Your objective is to determine the shortest possible route that visits each of the listed airports exactly once and returns to the starting point.

**Problem to Solve**

- Airports to visit: JBR, SLL, PAV, SVR, FNA, CKY, EBJ, APW, TRE
- Travel distances (in kilometers) between each pair of airports:
JBR to FNA: 8668
JBR to CKY: 8554
JBR to PAV: 8691
JBR to TRE: 6824
JBR to EBJ: 7556
JBR to APW: 11165
JBR to SLL: 13147
JBR to SVR: 8800
SLL to FNA: 7682
SLL to CKY: 7638
SLL to PAV: 12694
SLL to TRE: 6754
SLL to EBJ: 5821
SLL to APW: 15261
SLL to SVR: 10526
PAV to FNA: 5468
PAV to CKY: 5316
PAV to TRE: 8990
PAV to EBJ: 9253
PAV to APW: 16929
PAV to SVR: 13426
SVR to FNA: 9964
SVR to CKY: 9869
SVR to TRE: 4768
SVR to EBJ: 5233
SVR to APW: 17537
FNA to CKY: 1181
FNA to TRE: 5532
FNA to EBJ: 5638
FNA to APW: 19149
CKY to TRE: 5437
CKY to EBJ: 5550
CKY to APW: 19035
EBJ to TRE: 1304
EBJ to APW: 16293
APW to TRE: 15795
Please calculate the shortest tour and format your answer as follows: [Airport A, Airport B, Airport C, ..., Airport A]
user
{"directed": false, "multigraph": false, "graph": {}, "nodes": [{"name": "JBR", "id": 0}, {"name": "SLL", "id": 1}, {"name": "PAV", "id": 2}, {"name": "SVR", "id": 3}, {"name": "FNA", "id": 4}, {"name": "CKY", "id": 5}, {"name": "EBJ", "id": 6}, {"name": "APW", "id": 7}, {"name": "TRE", "id": 8}], "links": [{"weight": 8668, "source": 0, "target": 4}, {"weight": 8554, "source": 0, "target": 5}, {"weight": 8691, "source": 0, "target": 2}, {"weight": 6824, "source": 0, "target": 8}, {"weight": 7556, "source": 0, "target": 6}, {"weight": 11165, "source": 0, "target": 7}, {"weight": 13147, "source": 0, "target": 1}, {"weight": 8800, "source": 0, "target": 3}, {"weight": 7682, "source": 1, "target": 4}, {"weight": 7638, "source": 1, "target": 5}, {"weight": 12694, "source": 1, "target": 2}, {"weight": 6754, "source": 1, "target": 8}, {"weight": 5821, "source": 1, "target": 6}, {"weight": 15261, "source": 1, "target": 7}, {"weight": 10526, "source": 1, "target": 3}, {"weight": 5468, "source": 2, "target": 4}, {"weight": 5316, "source": 2, "target": 5}, {"weight": 8990, "source": 2, "target": 8}, {"weight": 9253, "source": 2, "target": 6}, {"weight": 16929, "source": 2, "target": 7}, {"weight": 13426, "source": 2, "target": 3}, {"weight": 9964, "source": 3, "target": 4}, {"weight": 9869, "source": 3, "target": 5}, {"weight": 4768, "source": 3, "target": 8}, {"weight": 5233, "source": 3, "target": 6}, {"weight": 17537, "source": 3, "target": 7}, {"weight": 1181, "source": 4, "target": 5}, {"weight": 5532, "source": 4, "target": 8}, {"weight": 5638, "source": 4, "target": 6}, {"weight": 19149, "source": 4, "target": 7}, {"weight": 5437, "source": 5, "target": 8}, {"weight": 5550, "source": 5, "target": 6}, {"weight": 19035, "source": 5, "target": 7}, {"weight": 1304, "source": 6, "target": 8}, {"weight": 16293, "source": 6, "target": 7}, {"weight": 15795, "source": 7, "target": 8}]}
You are required to solve the Travelling Salesman Problem for an undirected flight route network. Your objective is to determine the shortest possible route that visits each of the listed airports exactly once and returns to the starting point.

**Problem to Solve**

- Airports to visit: JBR, SLL, PAV, SVR, FNA, CKY, EBJ, APW, TRE
- Travel distances (in kilometers) between each pair of airports:
JBR to FNA: 8668
JBR to CKY: 8554
JBR to PAV: 8691
JBR to TRE: 6824
JBR to EBJ: 7556
JBR to APW: 11165
JBR to SLL: 13147
JBR to SVR: 8800
SLL to FNA: 7682
SLL to CKY: 7638
SLL to PAV: 12694
SLL to TRE: 6754
SLL to EBJ: 5821
SLL to APW: 15261
SLL to SVR: 10526
PAV to FNA: 5468
PAV to CKY: 5316
PAV to TRE: 8990
PAV to EBJ: 9253
PAV to APW: 16929
PAV to SVR: 13426
SVR to FNA: 9964
SVR to CKY: 9869
SVR to TRE: 4768
SVR to EBJ: 5233
SVR to APW: 17537
FNA to CKY: 1181
FNA to TRE: 5532
FNA to EBJ: 5638
FNA to APW: 19149
CKY to TRE: 5437
CKY to EBJ: 5550
CKY to APW: 19035
EBJ to TRE: 1304
EBJ to APW: 16293
APW to TRE: 15795
Please calculate the shortest tour and format your answer as follows: [Airport A, Airport B, Airport C, ..., Airport A]
test