In the compound shown, count the sets of chemically equivalent hydrogen atoms whose pKa is below 12. Use these approximate values: carboxylic acid O-H 4, phenolic O-H 8 to 10, CH2 flanked by two C=O groups 9 to 11, CH3 of a methyl ketone 20, aromatic C-H above 40. Each set of equivalent hydrogens counts once. Give the answer as an integer.

Numerical answer type, tolerance 0.5.