Since nuclear war is still very , very remote but still realistic possibility
there is time for all interested parties
to arrange a seat one day by very big table and
make arrangement in advance.
Lets assume that time of MAD day comes ,
which countries would like to participate and
who abstain and remain neutral in nuclear exchange.
Lets assume that all stockpile of nuclear warheads is going to be released onto interested in
exchange parties.
Some may prefer to remain neutral in hope to survive.
For example Switzerland. Gold will survive in deep vaults, but radioactive fallout? that another story.
New Zealand with old known antinuclear stance may have the greatest chance to survive. Scenario of MAD is highly hypothetical , abstract and impossible to imagine in real life,
but anyway some arrangements should be made in advance , in order to avoid surprises.
Countries now begging to deposit nuclear missiles on their land ,may think twice, as only those in possession or belonging to pacts will be subject to MAD.
Those non associated may be spared and hopefully repopulate Earth.

clock is ticking,
thebulletin.org/doomsday-clock/current-time/100 second could be still plenty for things you still want to do before Armageddon happen.
What would you do in your last 100 second since the world till exist before Armageddon ?
( for most its may depend how far the nearest toilet is
)