3^{1989}-1=(3^3)^{663}-1=(3^3-1)((3^3)^{662}+(3^3)^{661}+...+(3^3)+1)=26k
\Longrightarrow M(3^{4102}-3^{2113}, 3^{4105}-3^{2113})=26\cdot 3^{2113}