Six robots $A,B,C,D,E,F$ can contact as follows (directed): $B\!\to\!E$, $C\!\to\!B$; $A\!\to\!D$, $E\!\to\!D$, $F\!\to\!D$; $F\!\to\!C$; $D\!\to\!C$, $D\!\to\!E$; $A\!\to\!F$. Robots can relay messages along allowed contacts. What is the {minimum number of robots between $A$ and $B$ to send a message from $A$ to $B$?}
