how to optimized code with functions

[#1]

if(column(1)>=20 and column(1)<=39,1,

if(column(1)>=40 and column(1)<=59,2,

if(column(1)>=60 and column(1)<=79,3,

if(column(1)>=80 and column(1)<=99,4,

if(column(1)>=100 and column(1)<=119,5,

if(column(1)>=120 and column(1)<=139,6,

if(column(1)>=140 and column(1)<=159,7)))))))

[Gysbert_Wassenaar · Accepted solution]

try: floor(column(1)/20)