The strategy profile \((O_1O_3, O_2)\) is the unique pure-strategy sub-game perfect equilibrium (Selten 1975) of the game in Figure 17. Furthermore, the reasoning that we went through in the previous paragraphs is very close to backward induction algorithm. This algorithm can be used to calculate the sub-game perfect equilibrium in any perfect information game in which all players receive unique payoffs at each outcome.[13]  The algorithm runs as follows: