There are 50 students in Class 1, Class 6, who are elected as monitors. There are three candidates, Xiao Ming, Xiao Hua and Xiao Lin. It is stipulated that each student can only choose one of them, and he has to choose one. If among the votes of the top 40 classmates, Xiao Ming gets 18 votes, Xiao Hua gets 7 votes, and Xiao Lin gets 15 votes, how many votes does Xiao Ming need at least to ensure that Xiao Ming will be elected?
六1班50名同学选班长，有小明、小华和小林三个候选人，规定每个同学只能在他们三人中选1人，且不能不选．若在前40名同学的选票中，小明得了18票，小华得了7票，小林得了15票，要保证小明一定当选的话，小明至少还要得几票？
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