import java.io.BufferedReader import java.io.InputStream import java.io.InputStreamReader import java.lang.AssertionError import java.util.* import kotlin.math.abs import kotlin.math.max import kotlin.math.min val MOD = 998_244_353 fun packUGraph(n: Int, from: IntArray, to: IntArray): Array { val p = IntArray(n) val m = from.size for (i in 0 until m) { ++p[from[i]] ++p[to[i]] } val g = Array(n){IntArray(p[it])} for (i in 0 until m) { g[from[i]][--p[from[i]]] = to[i] g[to[i]][--p[to[i]]] = from[i] } return g } /** * (dist, parent, queue) * @param rt ルートノードを指定する。nullの場合は全ノード辿るまで繰り返す */ fun traceBfs(g: Array, rt: Int? = 0): Array { val n = g.size val q = IntArray(n) val d = IntArray(n) val p = IntArray(n){-2} var h = 0 var t = 0 fun bfs(rt: Int) { p[rt] = -1 q[t++] = rt d[rt] = 0 while (h < t) { val v = q[h++] for (i in g[v].indices) { // Listに変更したときこちらの方法でないとiterator生成して遅くなる val u = g[v][i] if (p[u] == -2) { p[u] = v q[t++] = u d[u] = d[v] + 1 } } } } if (rt != null) { bfs(rt) } else { for (v in 0 until n) { if (p[v] != -2) continue bfs(v) } } return arrayOf(d, p, q) } fun powMod(a: Long, n: Long, mod: Int): Long { if (n == 0L) return 1 val res = powMod(a * a % mod, n / 2, mod) return if (n % 2 == 1L) res * a % mod else res } class Solver(stream: InputStream, private val out: java.io.PrintWriter) { private val reader = BufferedReader(InputStreamReader(stream), 32768) fun solve() { val N = ni() val (from, to) = na2(N - 1, -1) val g = packUGraph(N, from, to) val (_, par, que) = traceBfs(g) val dp = LongArray(N) for (i in N - 1 downTo 0) { val v = que[i] dp[v]++ for (u in g[v]) { if (u == par[v]) continue dp[v] += dp[u] } } debug(dp) var cnt = 0L for (i in 0 until N - 1) { var v = from[i] // 親 var u = to[i] if (par[v] == u) { val t = v v = u u = t } val n = dp[u] // 子供側 val m = N - n cnt = (cnt + n*(n - 1)/2 + m*(m - 1)/2)%MOD // debug{"$n $m $cnt"} } debug{"$cnt"} val invn1 = powMod(N.toLong()-1, MOD.toLong()-2, MOD) val invn = powMod(N.toLong(), MOD.toLong()-2, MOD) val ans = cnt *invn1% MOD *invn%MOD *invn1%MOD *2%MOD // q = (n-1)*n*(n-1)/2 out.println(ans) } private val isDebug = try { // なんか本番でエラーでる System.getenv("MY_DEBUG") != null } catch (t: Throwable) { false } private var tokenizer: StringTokenizer? = null private fun next(): String { while (tokenizer == null || !tokenizer!!.hasMoreTokens()) { tokenizer = StringTokenizer(reader.readLine()) } return tokenizer!!.nextToken() } private fun ni() = next().toInt() private fun nl() = next().toLong() private fun ns() = next() private fun na(n: Int, offset: Int = 0): IntArray { return IntArray(n) { ni() + offset } } private fun nal(n: Int, offset: Int = 0): LongArray { val res = LongArray(n) for (i in 0 until n) { res[i] = nl() + offset } return res } private fun na2(n: Int, offset: Int = 0): Array { val a = Array(2){IntArray(n)} for (i in 0 until n) { for (e in a) { e[i] = ni() + offset } } return a } private inline fun debug(msg: () -> String) { if (isDebug) System.err.println(msg()) } /** * コーナーケースでエラー出たりするので、debug(dp[1])のように添え字付きの場合はdebug{}をつかうこと */ private inline fun debug(a: LongArray) { debug { a.joinToString(" ") } } private inline fun debug(a: IntArray) { debug { a.joinToString(" ") } } private inline fun debug(a: BooleanArray) { debug { toString(a) } } private inline fun toString(a: BooleanArray) = run{a.map { if (it) 1 else 0 }.joinToString("")} private inline fun debugDim(A: Array) { if (isDebug) { for (a in A) { debug(a) } } } private inline fun debugDim(A: Array) { if (isDebug) { for (a in A) { debug(a) } } } private inline fun debugDim(A: Array) { if (isDebug) { for (a in A) { debug(a) } } } /** * 勝手にimport消されるのを防ぎたい */ private fun hoge() { min(1, 2) max(1, 2) abs(-10) } private inline fun assert(b: Boolean) = run{if (!b) throw AssertionError()} private inline fun assert(b: Boolean, f: () -> String) = run{if (!b) throw AssertionError(f())} } fun main() { val out = java.io.PrintWriter(System.out) Solver(System.`in`, out).solve() out.flush() }