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: FDH, CCV, BMW, KAN, BIS, KHG, YGZ, SXX, ATD
- Travel distances (in kilometers) between each pair of airports:
FDH to KHG: 7002
FDH to YGZ: 9084
FDH to BMW: 3135
FDH to BIS: 7926
FDH to ATD: 15935
FDH to KAN: 5066
FDH to CCV: 17221
FDH to SXX: 9152
CCV to KHG: 11983
CCV to YGZ: 16690
CCV to BMW: 19776
CCV to BIS: 12085
CCV to ATD: 1567
CCV to KAN: 18570
CCV to SXX: 17039
BMW to KHG: 9633
BMW to YGZ: 11540
BMW to BIS: 9978
BMW to ATD: 18451
BMW to KAN: 5455
BMW to SXX: 9221
KAN to KHG: 9281
KAN to YGZ: 13247
KAN to BIS: 11349
KAN to ATD: 17245
KAN to SXX: 8260
BIS to KHG: 13966
BIS to YGZ: 5859
BIS to ATD: 13169
BIS to SXX: 8200
KHG to YGZ: 15460
KHG to ATD: 10658
KHG to SXX: 15963
YGZ to ATD: 17774
YGZ to SXX: 10720
SXX to ATD: 18278
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": "FDH", "id": 0}, {"name": "CCV", "id": 1}, {"name": "BMW", "id": 2}, {"name": "KAN", "id": 3}, {"name": "BIS", "id": 4}, {"name": "KHG", "id": 5}, {"name": "YGZ", "id": 6}, {"name": "SXX", "id": 7}, {"name": "ATD", "id": 8}], "links": [{"weight": 7002, "source": 0, "target": 5}, {"weight": 9084, "source": 0, "target": 6}, {"weight": 3135, "source": 0, "target": 2}, {"weight": 7926, "source": 0, "target": 4}, {"weight": 15935, "source": 0, "target": 8}, {"weight": 5066, "source": 0, "target": 3}, {"weight": 17221, "source": 0, "target": 1}, {"weight": 9152, "source": 0, "target": 7}, {"weight": 11983, "source": 1, "target": 5}, {"weight": 16690, "source": 1, "target": 6}, {"weight": 19776, "source": 1, "target": 2}, {"weight": 12085, "source": 1, "target": 4}, {"weight": 1567, "source": 1, "target": 8}, {"weight": 18570, "source": 1, "target": 3}, {"weight": 17039, "source": 1, "target": 7}, {"weight": 9633, "source": 2, "target": 5}, {"weight": 11540, "source": 2, "target": 6}, {"weight": 9978, "source": 2, "target": 4}, {"weight": 18451, "source": 2, "target": 8}, {"weight": 5455, "source": 2, "target": 3}, {"weight": 9221, "source": 2, "target": 7}, {"weight": 9281, "source": 3, "target": 5}, {"weight": 13247, "source": 3, "target": 6}, {"weight": 11349, "source": 3, "target": 4}, {"weight": 17245, "source": 3, "target": 8}, {"weight": 8260, "source": 3, "target": 7}, {"weight": 13966, "source": 4, "target": 5}, {"weight": 5859, "source": 4, "target": 6}, {"weight": 13169, "source": 4, "target": 8}, {"weight": 8200, "source": 4, "target": 7}, {"weight": 15460, "source": 5, "target": 6}, {"weight": 10658, "source": 5, "target": 8}, {"weight": 15963, "source": 5, "target": 7}, {"weight": 17774, "source": 6, "target": 8}, {"weight": 10720, "source": 6, "target": 7}, {"weight": 18278, "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: FDH, CCV, BMW, KAN, BIS, KHG, YGZ, SXX, ATD
- Travel distances (in kilometers) between each pair of airports:
FDH to KHG: 7002
FDH to YGZ: 9084
FDH to BMW: 3135
FDH to BIS: 7926
FDH to ATD: 15935
FDH to KAN: 5066
FDH to CCV: 17221
FDH to SXX: 9152
CCV to KHG: 11983
CCV to YGZ: 16690
CCV to BMW: 19776
CCV to BIS: 12085
CCV to ATD: 1567
CCV to KAN: 18570
CCV to SXX: 17039
BMW to KHG: 9633
BMW to YGZ: 11540
BMW to BIS: 9978
BMW to ATD: 18451
BMW to KAN: 5455
BMW to SXX: 9221
KAN to KHG: 9281
KAN to YGZ: 13247
KAN to BIS: 11349
KAN to ATD: 17245
KAN to SXX: 8260
BIS to KHG: 13966
BIS to YGZ: 5859
BIS to ATD: 13169
BIS to SXX: 8200
KHG to YGZ: 15460
KHG to ATD: 10658
KHG to SXX: 15963
YGZ to ATD: 17774
YGZ to SXX: 10720
SXX to ATD: 18278
Please calculate the shortest tour and format your answer as follows: [Airport A, Airport B, Airport C, ..., Airport A]
test