丟三落四

forgetful / empty-headed

to lose / to put aside / to throw

three / 3

to leave out / to be missing / to leave behind or forget to bring / to lag or fall behind

colloquial reading for 落[luo4] in certain compounds

to fall or drop / (of the sun) to set / (of a tide) to go out / to lower / to decline or sink / to lag or fall behind / to fall onto / to rest with / to get or receive / to write down / whereabouts / settlement

four / 4