#include <bits/stdc++.h>

using namespace std;

using i64=long long;
using u64=unsigned long long;
using db=double;
using vi=vector<int>;
using pii=pair<int,int>;

template<typename T>
inline T read(){
    T x=0,f=0;char ch=getchar();
    while(!isdigit(ch)) f|=(ch=='-'),ch=getchar();
    while(isdigit(ch)) x=(x*10)+(ch^48),ch=getchar();
    return !f?x:-x;
}

#define rdi read<int>
#define rdi64 read<i64>
#define fi first
#define se second
#define mp make_pair
#define pb push_back

const int N=5e5+10,MOD=998244353;

int n,k,v[N],a[N];
vi e[N];

int f[N];
void dfs(int x,int fa){
    f[x]=fa;
    for(auto y:e[x])
        if(y!=fa) dfs(y,x);
}

int main(){
#ifdef LOCAL
    freopen("1.in","r",stdin);
    freopen("1.out","w",stdout);
#endif
    n=rdi(),k=rdi();
    for(int i=1;i<=n;i++) v[i]=rdi();
    for(int i=1;i<=k;i++) a[i]=rdi();
    for(int i=1;i<n;i++){
        int x=rdi(),y=rdi();
        e[x].pb(y),e[y].pb(x);
    }
    dfs(1,0);
    i64 ans=1;
    for(int i=1;i<=n;i++)
        ans=ans*(v[i]-v[f[i]])%MOD;
    ans=(ans%MOD+MOD)%MOD;
    cout<<ans<<endl;
    return 0;
}