Veteran boxer M.C.Mary Kom on Tuesday assured herself of a medal as she entered the semi-finals of the Women's World Boxing Championship here.Olympic medallist Mary registered a comprehensive 5:0 victory over China's Wu Yu in the light flyweight (48 kg) category at the Indira Gandhi Sports Complex here.With this victory, the 35-year-old has assured herself of a seventh World Championship medal.Mary will now take on North Korea's Kim Hyang Mi on Thursday.