色多多在线观看播放-色多多在线观看高清免费-色多多在线观看视频-色多多在线看-欧美aaaaa性bbbbb小妇-欧美aaaav免费大片

The strongest principle of growth lies in human choice.

堅持是數學研究的關鍵，許多偉大的成果來自于長期的奮斗。

The mathematician's patterns, like the painter's or the poet's, must be beautiful; the ideas, like the colors or the words, must fit together in a harmonious way.