problem link : https://lightoj.com/problem/forming-the-council Solution : https://lightoj.com/submission/2067001 Can any one tell whats wrong in my code?

There is a 3*n grid which is to be filled with 3 different colors.How many ways can we do it if no column or row have all the cells of same color. N<=20000 and mod 1e9+7

https://www.hackerrank.com/contests/w22/challenges/number-of-sequences/problem Can any one help me with this problem on crt