person walks for 10 hours and walks a total of 45 kilometers. It is known that he walked 5 kilometers in the first hour, 3 kilometers in the last hour, and an integer number of kilometers in the remaining hours. Prove that: in the middle of 8 hours, There must have been two consecutive hours, and the person walked at least 10 kilometers.
某人步行10小时，共走45千米，已知他第1小时走5千米，最后1小时走3千米，其余各小时都走了整数千米，证明：在中间的8小时当中，一定存在连续的两小时，这人至少走了10千米．
<result>10</result>