The conversation between human and AI assistant.
[|Human|] Generate a regular expression that can match strings of any length consisting of only the letters a,b and c
[|AI|] The regular expression that can match strings of any length consisting of only the letters a, b, and c is: 

`^[abc]+$`
[|Human|] 
Generate a regular expression that can match strings of any length consisting of only the letters a,b and c