#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N,C,M;
vector<int> E[101010];
ll mo=998244353;

ll p[260][101010];

ll comb(ll N_, ll C_) {
	const int NUM_=400001;
	static ll fact[NUM_+1],factr[NUM_+1],inv[NUM_+1];
	if (fact[0]==0) {
		inv[1]=fact[0]=factr[0]=1;
		for (int i=2;i<=NUM_;++i) inv[i] = inv[mo % i] * (mo - mo / i) % mo;
		for (int i=1;i<=NUM_;++i) fact[i]=fact[i-1]*i%mo, factr[i]=factr[i-1]*inv[i]%mo;
	}
	if(C_<0 || C_>N_) return 0;
	return factr[C_]*fact[N_]%mo*factr[N_-C_]%mo;
}

ll dfs(int cur,int pre) {
	int NC=E[cur].size()-(cur!=pre);
	
	ll pat=1;
	ll sdp=1;
	FORR(e,E[cur]) if(e!=pre) {
		pat=pat*C%mo;
		sdp=sdp*dfs(e,cur)%mo;
	}
	
	if(cur!=pre) {
		for(int s=0;s<=NC-1;s++) if((s+1)*2>NC+1) {
			pat-=comb(NC,s)*p[C-1][NC-s]%mo;
		}
		for(int s=0;s<=NC;s++) if(s*2>NC+1) {
			pat-=(C-1)*comb(NC,s)%mo*p[C-1][NC-s]%mo;
		}
	}
	else {
		for(int s=0;s<=NC-1;s++) if(s*2>NC) {
			pat-=C*comb(NC,s)%mo*p[C-1][NC-s]%mo;
		}
	}
	pat=(pat%mo+mo)%mo;
	return pat*sdp%mo;
	
}

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	FOR(i,257) {
		p[i][0]=1;
		FOR(j,101000) p[i][j+1]=p[i][j]*i%mo;
	}
	
	cin>>N>>M;
	FOR(i,N-1) {
		cin>>x>>y;
		E[x-1].push_back(y-1);
		E[y-1].push_back(x-1);
	}
	ll ret=0;
	for(C=1;C<=M;C++) {
		ll pat=dfs(0,0);
		pat=pat*comb(M,C)%mo;
		if((C-M)%2==0) ret+=pat;
		else ret-=pat;
	}
	cout<<(ret%mo+mo)%mo<<endl;
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}