first three digit number
val = ( s . charAt ( 0 ) - '0' ) * 100 + ( s . charAt ( 1 ) - '0' ) * 10 + ( s . charAt ( 2 ) - '0' ) ; hm . put ( val , 1 ) ; for ( i = 3 ; i < s . length ( ) ; i ++ ) { val = ( val % 100 ) * 10 + s . charAt ( i ) - '0' ;