For a reaction $\mathrm{A} \rightarrow 2 \mathrm{~B}+\mathrm{C}$ the half lives are $100 \mathrm{~s}$ and $50 \mathrm{~s}$ when the concentration of reactant $\mathrm{A}$ is $0.5$ and $1.0 \mathrm{~mol} \mathrm{~L}^{-1}$ respectively. The order of the reaction is ______________ . (Nearest Integer)