互通有無 [－－－无]

Jyutping wu6 tung1 jau5 mou4
Pinyin hù tōng yǒu wú

Definitions (CC-CEDICT)
  1. (idiom) mutual exchange of assistance; to benefit from each other's strengths and make up each other's shortfalls; to reciprocate with material assistance; to scratch each other's back