Image forming system and control method

An image forming system comprising:

• an image forming apparatus;
• and
• a post-process apparatus configured to perform a designated post-process among a plurality of types of post-processes,
• the image forming apparatus including
• a controller configured to control the image forming apparatus and the post-process apparatus, and
• a detector configured to detect an attribute of paper fed from the image forming apparatus to the post-process apparatus for each sheet of paper,
• the post-process apparatus being configured to perform a post-process for each group of paper including designated number of sheets of paper,
• the controller being configured to
• store prohibition rule data which defines permission and prohibition of the post-process in accordance with the attribute of the paper for each type of the post-process,
• accept input of designation of a post-process to be performed by the post-process apparatus among the plurality of types of post-processes,
• determine for each sheet of the paper, whether the designated post-process is prohibited based on the prohibition rule data and the detected attribute of the paper, and
• determine, when the controller determines that the designated post-process is prohibited, whether paper which resulted in determination as the prohibition is a sheet of paper intermediate between a first sheet of paper and a last sheet of paper in the group of paper and have the image forming system perform a process in accordance with a result of determination.