I've read the supposed solution, it's dumb.
First you set up a boundary, then you apply the following rules:
First person who crosses the boundary, will be killed. All others will be granted their freedom.
If someone tries to take one for the team (purposely be the one killed), one of remaining will be killed at random and the rest will be granted their freedom.
How would you differentiate between someone "taking one for the team" and someone just making a run for it?
If a group tries to force someone across the boundary, or be the last man, one person at random from that group will be killed, and everyone else will be granted their freedom.
If a group attempts to cross the boundary simultaneously, one person at random from that group will be killed, and everyone else will be granted their freedom.
So a 99% chance of survival vs being held prisoner for life? Bye bye prisoners.
If you try to cross the boundary en mass, the last person to cross the barrier is killed and the rest will be granted their freedom.
Sucks to be last then. Bye bye everyone else.
D1 did leave out one important aspect from this dumb set up - they are all murderers, so you aren't meant to be granting anyone freedom anyway.