We need to determine the shortest possible route for a salesman who must visit a set of cities exactly once and return to the starting city. 
The objective is to minimize the total travel distance while ensuring that each city is visited exactly once.

Example input data:
1. cities.csv
city_id,city_name
1,CityA
2,CityB

2. distances.csv
from,to,distance
CityA,CityB,10
CityA,CityC,8
