The steps for constructing a line segment of given length are given in a jumbled order below:
1. Draw an arc on the line by keeping the pointed end of the compass on the point A. Mark the arc point as B.
2. Draw a line.
3. Extend the compass by keeping one end on the 0 cm mark and other at the given length on the ruler.
4. Take a point A anywhere on the line.
Which of the above steps comes third?