Look from right to left. 1 4, 4 to 2, 2 to 3. So 1 finally reaches 3.

Three to four, gone, so three to four.

4 to 2, 2 to 3 and 3 to 1, so 4 finally reaches 1.

Two to four, four to two, gone.

So 134

Individual textbooks are from left to right, similar to the algorithm.