No input validation, but yes to multi-stops

gistfile1.rb

n = %w( Times_Square 34th 28th 23th Union_Square 8th )
l = %w( 8th 6th Union_Square 3rd 1st )
six = %w( Grand_Central 33rd 28th 23rd Union_Square Astor_Place )
q = %w( Times_Square Herald_Square Union_Square Canal_St )

puts "What train on? [n, l, six, q]"

on_train = gets.chomp
case on_train
    when "n"
        @on = n
    when "l"
        @on = l
    when "six"
        @on = six
    when "q"
        @on = q
end

puts "which stop? #{@on}"
on_stop = gets.chomp

puts "what train off?"
off_train = gets.chomp
case off_train
    when "n"
        @off = n
    when "l"
        @off = l
    when "six"
        @off = six
    when "q"
        @off = q
end

puts "which stop? #{@off}"
off_stop = gets.chomp


intersections = []
@on.each do |get_on|
    @off.each do |get_off|
        if get_on == get_off
            intersections << get_off
        end
    end
end



if @on != @off
    @lowest_distance = 1000
    intersections.each do |intersect|
        first_dis = (@on.index(intersect) - @on.index(on_stop)).abs
        second_dis = (@off.index(intersect) - @off.index(off_stop)).abs
        dis = first_dis + second_dis
        if dis < @lowest_distance
            @lowest_distance = dis
        end
    end
    puts "your distance is #{@lowest_distance}"
else
    dis = (@on.index(off_stop) - @on.index(on_stop)).abs
    puts "your distace is #{dis}"
end