88888888x88888888: 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1

88888888x88888888: 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1

1 + 2 + 3 + 4 + 5 + 6 + 7 + 7 + 6 + 5 + 4 + 3 + 2 + 1 = 2 (1 + 7) + 2 (2 + 6) + 2 (3 + 5) + (8 + 4 + 4)) = 8 8888 8888 8888 (8 x8) = 11 11111 x 11 1111 = 1 123456787654321