[12,21,112,129,219,221,312,321,412,421,512,521,612,621,712,721,812,821,912,921,1012,1021,1112,1129,1299,1312,1321,1412,1421,1512,1521,1612,1621,1712,1721,1812,1821,1912,1921,2012,2021]