jacky
1st2nd3rd4th5th -- five --fifth6th7th8th eight eighth9th nine ninth从10到20 都加th,其中twelve twelfth 20 twenty twentieth 30 thirty thirtieth从21到29只要把个位改为序数词就可以了
1st 2nd 3rd 4th之后都是数字加th了
1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th 13th 14...20th 21st 22nd 23rd 24...30th 31st
