Ok, this one’s tough. I know there’s a bunch of you out there who love the math type puzzles, and this one’s going to be hard to crack:

The 400 soldiers of the 7th company are ready to march. They form a square of 20 meters x 20 meters.
Their mascot, a german shepherd dog, stands in the middle of the front line.
The 7th company starts to march at constant speed, and the mascot starts to walk the perimeter of the company clockwise at constant speed at the same time.
The dog is trained in such a way that, when the company has marched 20 meters, the mascot has walked the perimeter completely and is back in the middle of the front line.
The soldiers have marched 20 meters but, what is the distance the dog has walked?