#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; constexpr int INF = 1001001001; constexpr int mod = 1000000007; // constexpr int mod = 998244353; template inline bool chmax(T& x, T y){ if(x < y){ x = y; return true; } return false; } template inline bool chmin(T& x, T y){ if(x > y){ x = y; return true; } return false; } using Vec = vector; using Mat = vector; Mat Mul(const Mat& A, const Mat& B){ Mat C(A.size(), Vec(B[0].size())); for(int i = 0; i < (int)A.size(); ++i){ for(int k = 0; k < (int)A[0].size(); ++k){ for(int j = 0; j < (int)B.size(); ++j){ C[i][j] += A[i][k] * B[k][j]; } } } return C; } Mat Pow(Mat A, int n){ Mat B(A.size(), Vec(A.size())); for(int i = 0; i < (int)A.size(); ++i) B[i][i] = 1; while(n > 0){ if(n & 1) B = Mul(B, A); A = Mul(A, A); n >>= 1; } return B; } long double A[105]; int main(){ ios::sync_with_stdio(false); cin.tie(nullptr); int N; cin >> N; cout << fixed << setprecision(15); A[0] = 4; A[1] = 3; for(int i = 2; i <= N; ++i){ A[i] = (19 * A[i - 1] - 12 * A[i - 2]) / 4; } cout << A[N] << endl; return 0; }