# Very easy problem. Compute a few values w/ brute force or something, then check OEIS. # Part of: https://oeis.org/A001333 # Tells us: f(n) = (1/4) * Trace( [[0,0,1,0],[0,1,0,1],[1,0,2,0],[0,2,0,1]] ) # just write a program to compute this quickly # this sol takes something like ~O(log n) i think? x = input() + 1 mat = [[0,0,1,0],[0,1,0,1],[1,0,2,0],[0,2,0,1]] mod = 10**9+7 def egcd(a, b): if a == 0: return (b, 0, 1) else: g, y, x = egcd(b % a, a) return (g, x - (b // a) * y, y) def modinv(a, m): g, x, y = egcd(a, m) if g != 1: raise Exception('modular inverse does not exist') else: return x % m def matmult(mtx_a, mtx_b, mod): tpos_b = zip( *mtx_b) rtn = [[ sum( ea*eb for ea,eb in zip(a,b))%mod for b in tpos_b] for a in mtx_a] return rtn def trace(A): return sum(A[j][j] for j in range(len(A))) def matpow(A, p): ret = A for bit in bin(p)[3:]: ret = matmult(ret, ret, mod) if bit=='1': ret = matmult(ret, A, mod) return ret inv4 = modinv(4, mod) ans = trace(matpow(mat, x))%mod ans = (ans * inv4)% mod print ans