#include "leetcode.h" class Solution { public: int numOfWays(int n) { long a = 6, b = 6, c, d, mod = 1e9 + 7; for (int i = 1; i < n; ++i) { c = a * 3 + b * 2; d = a * 2 + b * 2; a = c % mod; b = d % mod; } return (a + b) % mod; } }; int main() { Solution obj; cout << obj.numOfWays(1); }