Safety must come first. During the coming summer vacation, some of us may travel to other places. To keep safe during the journey, we should .
①avoid eating raw(生的)and cold food
②obey the local traffic rules
③swim in the dangerous area
④never stretch our hands out of the window when taking a bus
⑤ tell strangers our personal information
，且
，
满足约束条件
的最大值为