This is LaTeX code:

[latex]
 
y=x-1 \Longrightarrow \left( y,y+1\right) \in \phi \Longrightarrow \left( y,x\right) \in \phi \\
y=x \Longrightarrow \left( y,y\right) \in \phi \Longrightarrow \left( y,x\right) \in \phi \\
y=x+1 \Longrightarrow \left( y,y-1\right) \in \phi \Longrightarrow \left( y,x\right) \in \phi 
[/latex]