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           RQ P                     9 S ≤ 12

                                             .S =9 .9

1+1+1 + 1     n( )                  n [AMC10B 2002] ( )
237n       n > 34 ( )                          .

     3                              2 n ()
                                                n < 21( )

0 < 41 + 1 < 41 + 1 < 2        1 + 1 + 1 = 41     :( )
    42 n 42 1                  2 3 7 42

                               . n = 42        .  41 + 1  =1
                                                  42 n

                                 m               [Aust.MC 2001] ( )
                                               12 ( ) 10 ( )
                         24, 42, m

m . 6, 15, m

30 ( )                   15 ( )

           . gcd(24, 42) = 6            :( )
                                           . gcd(24, m ) = 6
. lcm (6,15) = 30
. m = 30                 . 30      .m 6
                                 m . lcm (6, m ) = 30

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