There are two walls to be built. Area of one wall is twice that of the other. The labourers work on the larger wall for half a day. For the remaining half of the day, half of the labourers work on the larger wall, while the remaining work on the smaller wall. At the end of the day, the larger wall is completely built, while some portion of the smaller wall is left to be built, which is completed by one labourer the next day. How many labourers worked on the first day?