FM stations are not equal to AM stations, so it would not be a fair trade.
I'm saying that in addition to Entercom and Cumulus trading in Los Angeles and Houston, they could also trade in San Francisco with both companies being within the 5 FM and 3 AM ownership cap and Entercom receiving some of Cumulus' stations in other markets. Therefore, Entercom will only have to spin 2 more FMs in San Francisco.