A trisubstituted compound '$\mathrm{A}$', $\mathrm{C}_{10} \mathrm{H}_{12} \mathrm{O}_{2}$ gives neutral $\mathrm{FeCl}_{3}$ test positive. Treatment of compound 'A' with $\mathrm{NaOH}$ and $\mathrm{CH}_{3} \mathrm{Br}$ gives $\mathrm{C}_{11} \mathrm{H}_{14} \mathrm{O}_{2}$, with hydroiodic acid gives methyl iodide and with hot conc. $\mathrm{NaOH}$ gives a compound $\mathrm{B}, \mathrm{C}_{10} \mathrm{H}_{12} \mathrm{O}_{2}$. Compound 'A' also decolorises alkaline $\mathrm{KMnO}_{4}$. The number of $\pi$ bond/s present in the compound '$\mathrm{A}$' is _____________.