Literally: three – ten – six – plan
Alternately: Discretion is the better part of valor. Sometimes you just need to retreat, regroup, and try again another day. Run away.
Notes: Of the Thirty-Six Stratagems passed down from the Book of (Southern) Qi in Chinese antiquity, the thirty-sixth is flight, which (in contrast with surrender or compromise) is not considered a true loss and therefore, in a way, is the best of all of them.
A longer version of the phrase also exists: 三十六計逃げるに如かず (sanjuurokkei nigeru ni shikazu), “Of the Thirty-Six Stratagems, none compare with running away.”