Directed Graphs and Network Flows · Easy problem

A digraph $D$ has vertices $1,2,3,4,5$ and arcs $1\to2$, $2\to3$, $3\to4$, $4\to5$, $5\to1$, $1\to3$, $2\to4$. What is the largest value of $d^+(v) - d^-(v)$ over all five vertices $v$?