This prediction would be meaningless if the target molecule 𝑡 does not have the same reaction transformation at the reaction centre, at which the analogue reaction 𝑗 transforms from the reactant 𝑟 ",$ to the similar compound 𝑠 " . To exclude such invalid analogue reactions, graphs Next, at the graph of target molecule, 𝐺 ( , the algorithm subtracts the difference between the target product 𝑡 and the similar compound 𝑠 " L𝐺 * ! -𝑀𝐶𝑆 , $ !,# , , % ! N, and then uses the functional transformation of the analogue reaction L𝐺 + !,# -𝑀𝐶𝑆 , $ !,# , , % ! N to replace it and to determine the reactant, 𝑞 ",$ . Mathematically, the graph of an unknown reactant 𝐺 ' !,# is computed by Eq. 4.