Which size of sheet of paper is 0,5 m²

According to international standard ISO216 one of the three basic series of formats is A series, in which the ratio of the sides is 1 to √2, and the length of the sides are chosen so that the format A0 has a surface of 1m². Smaller formats result from the distribution of sheets in the middle of the longer side, thus maintaining proportions. As a result, the sheet A0 consists of 2 sheets A1, A1 of two sheets A2,