Graph Coloring · Easy problem

A compiler must assign registers to five live variables $v, w_1, w_2, w_3, w_4$. Variable $v$ is live for the whole routine, so it interferes with all four $w_i$. The $w_i$ are only live in a shifting window, so each interferes only with its immediate neighbor: $w_1\&w_2$, $w_2\&w_3$, $w_3\&w_4$. Two interfering variables cannot share a register. What is the fewest registers needed?