In view of the robot's super combat effectiveness, reconnaissance ability and protection ability, the army needs some robots to escort a group of people back to the camp. When robots and escorted people come to a Grand Canyon, they need to cross a single log bridge. They can only march in column. Due to the limited length of the single log bridge, the total number of marching robots and people on the bridge deck should not exceed M. To ensure the relative safety of people, there must be at least one robot between every two people in the column. For example, when M is 3, there are five marching modes: human robot human, human robot robot, robot human robot, robot robot human and robot robot robot.

If we give the number of marches that a single log bridge can bear at the same time, in order to achieve the fastest March, how many different marching schemes are there when the single log bridge is required to pass through the full capacity each time?