#define MD 998244353
int@n,@(a,b)--[n-1];
Mint t[n],u=1;
rep(i,n){
	t[i]=u;
	u+=u;
}
t[n-1]-=2;
graph g;
g.setEdge(n,n-1,a,b);
wt(sum[i,0,n](t[g.es[i]]));