@ @SW@ @†a‡Èÿa@ @ + TW O F OU R 3() 2( ) 1( ) 0 () [AMC8 2003] ( ) 2000 1000 25 20 15 4() 3( ) 2( ) 1 () : 12 [AMC8 2004] ( ) 864 ( ) 17 . 72 204 ( ) 102 ( ) 6 ()