An equimolar mixture of pent-2-ene (both E and Z), 2-methylbut-2-ene, 3-methylpent-2-ene and hex-3-ene (both E and Z) is subjected to ozonolysis with reductive work-up. How many DISTINCT carbonyl compounds are obtained in total? (Count each different compound once; E/Z isomers of an alkene give the same products.)

Numerical answer type, tolerance 0.5.