On a closed track, clockwise, there are five boxes and , and the length of the track section between boxes and is km, between and - km, between and - km, between and - km, and between and - km. On the track, they drive in a clockwise direction, the race always begins and ends in the box. What box did you start from if the length of the race was exactly km?
EE-MO 1998
Estonian Mathematical Olympiad 1998.