Build a bridge over the "rift," using the bricks in the way you see on the picture!
Build the two pillars separately, so that they remain stable and bear the last brick in the middle!
The key is that the whole (resultant) center of gravity of the pillar's bricks remain on the shore.
The center of mass (the center of gravity) of a system behaves in a way, as if the system's mass (gravity) were concentrated in that point. If we support the center of gravity, the whole system is standing still. If the center of gravity of the system consisting of the bricks remains on the shore, the bridge is standing still.
The center of gravity of the human body is at the pelvic. This is why high jumpers concentrate on their hips to get over the bar.
