Below is a trace of the call repeatDigits(-348):
        repeatDigits(-348)
            is < 0, so execute first branch
            compute repeatDigits(-n), which is repeatDigits(348)
            |   not < 0, not < 10, so execute third branch
            |   compute repeatDigits(34)
            |   |   not < 0, not < 10, so execute third branch
            |   |   compute repeatDigits(3)
            |   |   |   not < 0, but is < 10, so execute second branch
            |   |   |   return n * 11 (33)
            |   |   compute repeatDigits(4)
            |   |   |   not < 0, but is < 10, so execute second branch
            |   |   |   return n * 11 (44)
            |   |   return first * 100 + second (33 * 100 + 44 = 3344)
            |   compute repeatDigits(8)
            |   |   not < 0, but is < 10, so execute second branch
            |   |   return n * 11 (88)
            |   return first * 100 + second (3344 * 100 + 88 = 334488)
            return the negation of that result (-334488)