func main() var n: int :: cui@inputInt() var ans: modInt :: (#modInt).init(10, 1000000007) do ans.pow(n) do ans.mul(4) do ans.sub(1) do ans.div(3) do cui@print("\{ans}\n") ; val, mod, a, b: 0 to 2 ^ 31. class modInt() var val: int var mod: int +func init(val: int, mod: int): modInt do me.val :: val % mod do me.mod :: mod ret me end func +func add(a: int): modInt do me.val :+ a if(me.val >= me.mod) do me.val :- me.mod end if ret me end func +func sub(a: int): modInt if(me.val < a) do me.val :+ me.mod end if do me.val :- a ret me end func +func mul(a: int): modInt do me.val :: me.val * a % me.mod ret me end func +func div(a: int): modInt do me.val :: me.val * me.modPow(a, me.mod - 2) % me.mod ret me end func +func pow(a: int): modInt do me.val :: me.modPow(me.val, a) ret me end func +*func toStr(): []char ret "\{me.val}" end func func modPow(a: int, b: int): int if(b = 0) ret 1 end if var res: int :: me.modPow(a, b / 2) do res :: res * res % me.mod if(b % 2 = 1) do res :: res * a % me.mod end if ret res end func end class end func