Problem with animation cycles

Hello, ladies and gentlmen, I faced some problem with animation: I have quite a simple animation of a walking monster, and it has too sharp transformation when the final frame is over and the first begins (in shot, it's not realistic between the cycles of this animation). It looks like a monster has a tiny stop at each major pose (when left or right arm/leg reaches its extreme position).

I tried to edit graphs so that it wouldn't have any local extreme points on the global way of animation (and now it seems that they are all quite smooth!), but I still have that auful "start" and "end" points.

I would be very, VERY grateful for any piece of advice!

P.S. In attached video you can notice the problem that if you set the video to be autorepeated.

MY BLEND FILE