An input assistance device according to an exemplary aspect of the present invention includes: an operation storing unit which stores a plurality of types of operations targeting a display object arranged in a shared screen shared by a plurality of terminal devices; an operation history storing unit which stores a history operation that is a performed operation targeting an arranged object which is the display object stored in display object storing unit and arranged in the shared screen, in order of performance of the history operation, and stores participating user identifiers that are identifiers of users of the plurality of terminal devices; and an operation score deriving unit which derives an operation probability being a probability that a target user performs next time a candidate operation being the operation stored in the operation storing unit, based on a target user identifier, the history operation, and the participating user identifier.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. An input assistance device, comprising: an operation storing unit which stores a plurality of types of operations targeting a display object arranged in a shared screen shared by a plurality of terminal devices; an operation history storing unit which stores a history operation that is a performed operation targeting an arranged object which is the display object stored in display object storing unit and arranged in the shared screen, in order of performance of the history operation, and stores participating user identifiers that are identifiers of users of the plurality of terminal devices; and an operation score deriving unit which derives an operation probability being a probability that a target user who is a user of a target terminal device in the plurality of terminal devices performs next time a candidate operation being the operation stored in the operation storing unit, based on a target user identifier being an identifier of the target user, the history operation, and the participating user identifier. 2. The input assistance device according to claim 1, wherein the operation history storing unit stores an operating user identifier that is an identifier of the user performing the history operation, the operating user identifier being associated with the history operation, and the operation score deriving unit derives the operation probability based on the target user identifier that is the identifier of the target user, the history operation, and the operating user identifier associated with the history operation. 3. The input assistance device according to claim 1, wherein the display object storing unit stores an arrangement position that is a position where the arranged object is arranged in the shared screen, the arrangement position being associated with the arranged object, and the operation score deriving unit derives the operation probability based on the arranging position. 4. The input assistance device according to claim 1, wherein the display object storing unit further stores an arrangement position that is a position where the arranged object is arranged in the shared screen, and a generation time when the arranged object is generated, the arrangement position and the generation time being associated with the arranged object, the input assistance device further comprises: an object group generating unit which generates, from the display objects stored in the display object storing unit, an object group including at least a part of the display objects, so that difference in at least one of the arrangement position and the generation time between each of the display objects included in the object group and at least one of other display objects included in the object group satisfies a condition; and a learning unit which derives a parameter to derive the operation probability based on the history operation targeting the display object included in the object group, and the operation score deriving unit derives the operation probability by using the derived parameter based on the history operation targeting the arranged object that is included in the object group including the arranged object targeted by a latest history operation. 5. The input assistance device according to claim 4, wherein the operation score deriving unit derives the operation probability based on the arranging position. 6. The input assistance device according to claim 1, wherein the operation history storing unit stores an operation time when the history operation on the arranged object is performed, the operation time being associate with history operation, and the operation probability deriving unit derives the operation probability based on the operation time. 7. The input assistance device according to claim 1, further comprising: an operation receiving unit which receives the operation from the terminal device, updates the arranged object based on the received operation, and stores the received operation as the history operation in the operation history storing unit; a shared screen outputting unit which outputs the shared screen in which the display object is arranged to the target terminal; and an operation recommending unit which outputs information recommending inputting the candidate operation which is selected according to the derived operation probability of the candidate operation to the target terminal device. 8. An information processing system including the input assistance device according to claim 1, comprising: the plurality of terminals. 9. An input assisting method, comprising: storing a plurality of types of operations targeting a display object arranged in a shared screen shared by a plurality of terminal devices in operation storing unit; storing a history operation that is a performed operation targeting an arranged object that is the display object stored in display object storing unit and arranged in the shared screen, in order of performance of the history operation, and storing participating user identifiers that are identifiers of users of the plurality of terminal devices in an operation history storing unit; and deriving an operation probability being a probability that a target user who is a user of a target terminal device in the plurality of terminal devices performs next time a candidate operation being the operation stored in the operation storing unit, based on a target user identifier being an identifier of the target user, the history operation, and the participating user identifier. 10. A non-transitory computer-readable recording medium storing an input assistance program causing a computer to operate as: operation storing unit which stores a plurality of types of operations targeting a display object arranged in a shared screen shared by a plurality of terminal devices; operation history storing unit which stores a history operation that is a performed operation targeting an arranged object that is the display object stored in display object storing unit and arranged in the shared screen, in order of performance of the history operation, and for storing participating user identifiers that are identifiers of users of the plurality of terminal devices; and operation score deriving unit which derives an operation probability being a probability that a target user who is a user of a target terminal device in the plurality of terminal devices performs next time a candidate operation being the operation stored in the operation storing unit, based on a target user identifier being an identifier of the target user, the history operation, and the participating user identifier.