#pragma GCC optimize ("Ofast") #include using namespace std; #define MD (998244353U) void*wmem; char memarr[96000000]; template inline void walloc1d(T **arr, int x, void **mem = &wmem){ static int skip[16] = {0, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1}; (*mem) = (void*)( ((char*)(*mem)) + skip[((unsigned long long)(*mem)) & 15] ); (*arr)=(T*)(*mem); (*mem)=((*arr)+x); } template inline void walloc1d(T **arr, int x1, int x2, void **mem = &wmem){ walloc1d(arr, x2-x1, mem); (*arr) -= x1; } struct Modint{ unsigned val; Modint(){ val=0; } Modint(int a){ val = ord(a); } Modint(unsigned a){ val = ord(a); } Modint(long long a){ val = ord(a); } Modint(unsigned long long a){ val = ord(a); } inline unsigned ord(unsigned a){ return a%MD; } inline unsigned ord(int a){ a %= (int)MD; if(a < 0){ a += MD; } return a; } inline unsigned ord(unsigned long long a){ return a%MD; } inline unsigned ord(long long a){ a %= (int)MD; if(a < 0){ a += MD; } return a; } inline unsigned get(){ return val; } inline Modint &operator++(){ val++; if(val >= MD){ val -= MD; } return *this; } inline Modint &operator--(){ if(val == 0){ val = MD - 1; } else{ --val; } return *this; } inline Modint operator++(int a){ Modint res(*this); val++; if(val >= MD){ val -= MD; } return res; } inline Modint operator--(int a){ Modint res(*this); if(val == 0){ val = MD - 1; } else{ --val; } return res; } inline Modint &operator+=(Modint a){ val += a.val; if(val >= MD){ val -= MD; } return *this; } inline Modint &operator-=(Modint a){ if(val < a.val){ val = val + MD - a.val; } else{ val -= a.val; } return *this; } inline Modint &operator*=(Modint a){ val = ((unsigned long long)val*a.val)%MD; return *this; } inline Modint &operator/=(Modint a){ return *this *= a.inverse(); } inline Modint operator+(Modint a){ return Modint(*this)+=a; } inline Modint operator-(Modint a){ return Modint(*this)-=a; } inline Modint operator*(Modint a){ return Modint(*this)*=a; } inline Modint operator/(Modint a){ return Modint(*this)/=a; } inline Modint operator+(int a){ return Modint(*this)+=Modint(a); } inline Modint operator-(int a){ return Modint(*this)-=Modint(a); } inline Modint operator*(int a){ return Modint(*this)*=Modint(a); } inline Modint operator/(int a){ return Modint(*this)/=Modint(a); } inline Modint operator+(long long a){ return Modint(*this)+=Modint(a); } inline Modint operator-(long long a){ return Modint(*this)-=Modint(a); } inline Modint operator*(long long a){ return Modint(*this)*=Modint(a); } inline Modint operator/(long long a){ return Modint(*this)/=Modint(a); } inline Modint operator-(void){ Modint res; if(val){ res.val=MD-val; } else{ res.val=0; } return res; } inline operator bool(void){ return val!=0; } inline operator int(void){ return get(); } inline operator long long(void){ return get(); } inline Modint inverse(){ int a = val; int b = MD; int u = 1; int v = 0; int t; Modint res; while(b){ t = a / b; a -= t * b; swap(a, b); u -= t * v; swap(u, v); } if(u < 0){ u += MD; } res.val = u; return res; } inline Modint pw(unsigned long long b){ Modint a(*this); Modint res; res.val = 1; while(b){ if(b&1){ res *= a; } b >>= 1; a *= a; } return res; } inline bool operator==(int a){ return ord(a)==val; } inline bool operator!=(int a){ return ord(a)!=val; } } ; inline Modint operator+(int a, Modint b){ return Modint(a)+=b; } inline Modint operator-(int a, Modint b){ return Modint(a)-=b; } inline Modint operator*(int a, Modint b){ return Modint(a)*=b; } inline Modint operator/(int a, Modint b){ return Modint(a)/=b; } inline Modint operator+(long long a, Modint b){ return Modint(a)+=b; } inline Modint operator-(long long a, Modint b){ return Modint(a)-=b; } inline Modint operator*(long long a, Modint b){ return Modint(a)*=b; } inline Modint operator/(long long a, Modint b){ return Modint(a)/=b; } inline int my_getchar_unlocked(){ static char buf[1048576]; static int s = 1048576; static int e = 1048576; if(s == e && e == 1048576){ e = fread_unlocked(buf, 1, 1048576, stdin); s = 0; } if(s == e){ return EOF; } return buf[s++]; } inline void rd(int &x){ int k; int m=0; x=0; for(;;){ k = my_getchar_unlocked(); if(k=='-'){ m=1; break; } if('0'<=k&&k<='9'){ x=k-'0'; break; } } for(;;){ k = my_getchar_unlocked(); if(k<'0'||k>'9'){ break; } x=x*10+k-'0'; } if(m){ x=-x; } } struct MY_WRITER{ char buf[1048576]; int s; int e; MY_WRITER(){ s = 0; e = 1048576; } ~MY_WRITER(){ if(s){ fwrite_unlocked(buf, 1, s, stdout); } } } ; MY_WRITER MY_WRITER_VAR; void my_putchar_unlocked(int a){ if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){ fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout); MY_WRITER_VAR.s = 0; } MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a; } inline void wt_L(char a){ my_putchar_unlocked(a); } inline void wt_L(int x){ int s=0; int m=0; char f[10]; if(x<0){ m=1; x=-x; } while(x){ f[s++]=x%10; x/=10; } if(!s){ f[s++]=0; } if(m){ my_putchar_unlocked('-'); } while(s--){ my_putchar_unlocked(f[s]+'0'); } } inline void wt_L(Modint x){ int i; i = (int)x; wt_L(i); } struct graph{ int N; int*es; int**edge; void setEdge(int N__, int M, int A[], int B[], void **mem = &wmem){ int i; N = N__; walloc1d(&es, N, mem); walloc1d(&edge, N, mem); for(i=(0);i<(N);i++){ es[i] = 0; } for(i=(0);i<(M);i++){ es[A[i]]++; es[B[i]]++; } for(i=(0);i<(N);i++){ walloc1d(&edge[i], es[i], mem); } for(i=(0);i<(N);i++){ es[i] = 0; } for(i=(0);i<(M);i++){ edge[A[i]][es[A[i]]++] = B[i]; edge[B[i]][es[B[i]]++] = A[i]; } } void SubTreeSize(int root, int res[], void *mem = wmem){ int i; int j; int k; int m; int*q; int qs = 0; int qe = 1; walloc1d(&q,N,&mem); for(i=(0);i<(N);i++){ res[i] = -1; } res[root] = 0; q[0] = root; while(qs < qe){ i = q[qs++]; for(j=(0);j<(es[i]);j++){ k = edge[i][j]; if(res[k]==0){ continue; } res[k] = 0; q[qe++] = k; } } for(m=(N)-1;m>=(0);m--){ i = q[m]; res[i] = 1; for(j=(0);j<(es[i]);j++){ k = edge[i][j]; res[i] += res[k]; } } } } ; int N; int A[100000]; int B[100000]; graph g; int sz[100000]; int main(){ int i; wmem = memarr; Modint res = 0; rd(N); { int Lj4PdHRW; for(Lj4PdHRW=(0);Lj4PdHRW<(N-1);Lj4PdHRW++){ rd(A[Lj4PdHRW]);A[Lj4PdHRW] += (-1); rd(B[Lj4PdHRW]);B[Lj4PdHRW] += (-1); } } g.setEdge(N,N-1,A,B); g.SubTreeSize(0,sz); for(i=(1);i<(N);i++){ res += (long long) sz[i] * (sz[i] - 1); } for(i=(1);i<(N);i++){ res += (long long) (N - sz[i]) * (N - sz[i] - 1); } res /= (long long) N * (N-1); res /= N-1; wt_L(res); wt_L('\n'); return 0; } // cLay version 20210508-1 [beta] // --- original code --- // #define MD 998244353 // int N, A[1d5], B[1d5]; // graph g; // int sz[]; // { // Modint res = 0; // rd(N,(A--,B--)(N-1)); // g.setEdge(N,N-1,A,B); // g.SubTreeSize(0,sz); // rep(i,1,N) res += (ll) sz[i] * (sz[i] - 1); // rep(i,1,N) res += (ll) (N - sz[i]) * (N - sz[i] - 1); // res /= (ll) N * (N-1); // res /= N-1; // wt(res); // }