ip = "192.168.73.173"
nm = "255.255.255.224"

ip_bits = []
nm_bits = []

ip.split(".").each do |bits|
        ip_bits << ("%08b" % bits)
end

nm.split(".").each do |bits|
        nm_bits << ("%08b" % bits)
end

network = []

m = 0
while m < 4
        block = ""
        n = 0
        while n < 8
                block += (ip_bits[m].split("")[n].to_i & nm_bits[m].split("")[n].to_i).to_s
                n += 1
        end
        network << block.to_i(2)
        m += 1
end

puts network.join(".")