ok 1 - '1-2-3-4' => [1, 2, 3, 4]
ok 2 - '1--2-3-4' => [1, -2, 3, 4]
ok 3 - '-1-2-3-4' => [-1, 2, 3, 4]
ok 4 - '1-2-3--4' => [1, 2, 3, -4]
ok 5 - '-1--2--3--4' => [-1, -2, -3, -4]
ok 6 - '15--20-25--30' => [15, -20, 25, -30]
1..6