The southernmost length of the living room: 7+5-4-2-2=4 (meters)

The contact length between the living room, the bathroom and the north of the kitchen is 2X2=4 (meters).

The living room is symmetrical left and right, and the length of the side contacting with the children's room is 2X2=4 (meters).

The contact length between the living room and the east of the bathroom and the west of the kitchen is 3X2=6 (meters).

It adds up to 26 meters.