dhcp client script / help needed

RouterOS Scripting
1

I need to add to the /ip firewall address-list the network address that has been recved from dhcp client.

:global ipaddress [/ip dhcp-client get [/ip dhcp-client find where interface=e1_WAN] address]
result: 172.16.14.14/28
i need: 172.16.14.0/28

any ideas?

2

I will ask differently, how to reparse the text:
172.16.14.14/28
to receive:
172.16.14.0/28

/p