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SMO 2011 Junior Round 1 Question 25

SMO · SMO 2011 Junior Round 1

Question 25

If the 13th of any particular month falls on a Friday, we call it Friday the 13th. It is known that Friday the 13th occurs at least once every calendar year. If the longest interval between two consecutive occurrences of Friday the 13th is $x$ months, find $x$.