Limits and Continuity · Challenge problem

A function $f$ is continuous on $[0,6]$, and $f(0)=2$, $f(1)=-1$, $f(2)=5$, $f(3)=1$, $f(4)=6$, $f(5)=2$, $f(6)=9$. What is the least number of solutions that the equation $f(x)=x$ must have in $[0,6]$?