#include <bits/stdc++.h>
template <int MOD>
struct ModInt {
  using lint = long long;
  int val;
  ModInt(lint v = 0) : val(v % MOD) {
    if (val < 0) val += MOD;
  };
  ModInt operator+() const { return ModInt(val); }
  ModInt operator-() const { return ModInt(MOD - val); }
  ModInt inv() const { return this->pow(MOD - 2); }
  ModInt operator+(const ModInt& x) const { return ModInt(*this) += x; }
  ModInt operator-(const ModInt& x) const { return ModInt(*this) -= x; }
  ModInt operator*(const ModInt& x) const { return ModInt(*this) *= x; }
  ModInt operator/(const ModInt& x) const { return ModInt(*this) /= x; }
  ModInt pow(lint n) const {
    auto x = ModInt(1);
    auto b = *this;
    while (n > 0) {
      if (n & 1) x *= b;
      n >>= 1;
      b *= b;
    }
    return x;
  }
  ModInt& operator+=(const ModInt& x) {
    if ((val += x.val) >= MOD) val -= MOD;
    return *this;
  }
  ModInt& operator-=(const ModInt& x) {
    if ((val -= x.val) < 0) val += MOD;
    return *this;
  }
  ModInt& operator*=(const ModInt& x) {
    val = lint(val) * x.val % MOD;
    return *this;
  }
  ModInt& operator/=(const ModInt& x) { return *this *= x.inv(); }
  bool operator==(const ModInt& b) const { return val == b.val; }
  bool operator!=(const ModInt& b) const { return val != b.val; }
  friend std::istream& operator>>(std::istream& is, ModInt& x) noexcept {
    return is >> x.val;
  }
  friend std::ostream& operator<<(std::ostream& os, const ModInt& x) noexcept {
    return os << x.val;
  }
};
constexpr int MOD = 998244353;
using mint = ModInt<MOD>;
template <class Cost = int>
struct Edge {
  int src, dst;
  Cost cost;
  Edge(int src = -1, int dst = -1, Cost cost = 1)
      : src(src), dst(dst), cost(cost){};
  bool operator<(const Edge<Cost>& e) const { return this->cost < e.cost; }
  bool operator>(const Edge<Cost>& e) const { return this->cost > e.cost; }
};
template <class Cost = int>
using Graph = std::vector<std::vector<Edge<Cost>>>;
void solve() {
  int n;
  std::cin >> n;
  Graph<> graph(n);
  for (int i = 0; i < n - 1; ++i) {
    int u, v;
    std::cin >> u >> v;
    --u, --v;
    graph[u].emplace_back(u, v);
    graph[v].emplace_back(v, u);
  }
  std::vector<std::vector<mint>> dps(n, std::vector<mint>(3, 1));
  std::function<void(int, int)> dfs = [&](int v, int p) -> void {
    auto& dp = dps[v];
    for (auto e : graph[v]) {
      int u = e.dst;
      if (u == p) continue;
      dfs(u, v);
      const auto& sdp = dps[u];
      dp[0] *= sdp[0] * 2 + sdp[1] * 2 + sdp[2] * 3;
      dp[1] *= sdp[0] * 2 + sdp[1] * 1 + sdp[2] * 2;
      dp[2] *= sdp[0] * 1 + sdp[1] * 1 + sdp[2] * 1;
    }
    dp[0] -= dp[2];
    dp[1] -= dp[2];
  };
  dfs(0, -1);
  std::cout << std::accumulate(dps[0].begin(), dps[0].end(), mint(0)) - 1
            << std::endl;
}
int main() {
  std::cin.tie(nullptr);
  std::cout.tie(nullptr);
  std::ios::sync_with_stdio(false);
  solve();
  return 0;
}
