Directed Graphs and Network Flows · Medium problem

A digraph has vertices $1,\dots,6$ and arcs $1\to2$, $2\to1$, $3\to4$, $4\to3$, $5\to6$, $6\to5$, $1\to3$, $3\to5$, $2\to5$. How many arcs does its condensation have?