What would the script below output in the Python console?

listb $=$ list$($range$(0,21,3))$

listc $=$ listb$[-1]$

print$(\text{'}$listc is$\text{'},$ listc$)$

listc is $21$

listc is $18$

listc is $15$

listc is $3$

listc is $20$

listc is $1$

listc is $0$