The information processing device 1X mainly includes an acquisition means 16Xa and a transition sequence determination means 16Xb. The acquisition means 16Xa acquires a first combination between sellers and buyers conducting transactions and a second combination between the sellers and the buyers differing from the first combination. The transition sequence determination means 16Xb determines a transition sequence of combinations between the sellers and the buyers, the transition sequence being generated in a process of making a transition, per basic operation for changing the combinations between the sellers and the buyers, from the first combination to the second combination, each combination of the transition sequence making a profit of a mediator equal to or larger than a threshold value, the mediator mediating the transactions.