Seven different coloured boxes, red, yellow, green, blue, magenta, purple, and orange, are kept one above the other but not necessarily in the same order. There are only four boxes between the yellow box and the blue box. The red box is just below the blue box and just above the purple box. The green box is kept at the bottom-most position.

If the position of the purple box is exchanged with the box that is just below it, then how many boxes will be there between the green and purple boxes?