[tex]\begin{array}{c|c}\sf13,39,27&\sf3\\\sf13,13,9&\sf3\\\sf13,13,3&\sf3\\\sf13,13,1&\sf13\\\sf1,1,1&\boxed{1}\end{array}[/tex]
[tex]\boxed{\boxed{\sf m\cdot d\cdot c(13,39,27)=1}}[/tex]
