10 + 9 • { 8 + 7 • ( 4 + 3 • ( 2 + 1 ) ] } =
10 + 9 [ 8 + 7 ( 4 + 3 • 3 ) ] =
10 + 9 [ 8 + 7 ( 4 + 9 ) ] =
10 + 9 ( 8 + 7 • 13 ) =
10 + 9 ( 8 • 91 ) =
10 + 9 • 99 =
10 + 891 =
901
