= 20 or 21 or 22???

how would i give multiple values in 1 line?
if ( mana = 20 or 21 or 22)
{
do something
}
i tried with commas and periods, but it didnt work
if ( mana = 20 or 21 or 22)
{
do something
}
i tried with commas and periods, but it didnt work