How to read JSON with BOOST?

Question

JSON

How to parse this JSON using boost::ptree, c++ so that you can pull out the pairs after b and the pairs after a if there are any?

{"stream":"[email protected]@100ms","data":{"e":"depthUpdate","E":1604921041149,"s":"BTCUSDT","U":6511117685,"u":6511117709,"b":,"a":}}