Split text in certain length

Hi, need help todo something, in my app people can put numbres in a text box (e.g. 1345654567678765), what I want to do is get these numbers and put a space every four digits like this (1345 6545 6767 8765) and them turn it into a variable… how can I do this?

You can use segment block to get desired length text.

segment:length is negative (-13) i have a problem how solve

The error says all.
Length should not be negative.