Notice how the man who enters on right side makes his turn to go up the stair case. He adjusts his weight ever so slightly to go around the man who just stood up. Normally the head leads and the body follows, but in this case, the guy seems to know where he is going and that he is pre-occupied with something in the distance. (THiNKING) Watch how he uses his hand to go up the stairs. Does he really need it? Perhaps he's Tired.
Another interesting thing is that another man zips up the steps and they both get to the top at exactly the same time. Notice how the second man anticipates downward before he reaches the first step. This is nice contrast in action. Any how, lots of other subtle stuff here with these two and other characters.