sub gen3 {
    my $constraints = shift;
    my @rands = map $_->{ mid } - $_->{ sd }, @$constraints;
    my @limits = map $_->{ mid } + $_->{ sd }, @$constraints;
    my $maxChange = min map $_->{ sd }, @$constraints;
    my $remainder = 100 - sum @rands;
    while( $remainder ) {
        my $target = int rand @rands;
        my $addition = 1+ int rand min( $remainder, $maxChange );
        next if $rands[ $target ] + $addition > $limits[ $target ];
        $rands[ $target ] += $addition;
        $remainder -= $addition;
    }
    return @rands;
}