Imaris
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and there could be many possibilities:
he hit with the handle, not the blade
Igor turned out to be a robot
Volodya missed
he hit him in the hand, and no one has ever died from that
Igor knew that Volodya would want to kill him, so he put on a bulletproof vest
the knife was made of wood!
Actually, my task is too complicated.
Perhaps the conditions should have somehow hinted at a ship, a wife, the past, etc.