一回生二回熟

yī huí shēng èr huí shú

unfamiliar at first, but well accustomed soon enough (idiom)

一

yī

one

回

huí

variant of 迴|回[hui2]

生

shēng

to be born

二

èr

two

回

huí

variant of 迴|回[hui2]

熟

shú

ripe; mature