#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize ("Ofast")
#pragma GCC target ("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
using namespace std;


#define TRACE

#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
	cerr << name << " : " << arg1 << std::endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
	const char* comma = strchr(names + 1, ',');cerr.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...);
}
#else
#define trace(...)
#endif

#define rep(i, n)    for(int i = 0; i < (n); ++i)
#define repA(i, a, n)  for(int i = a; i <= (n); ++i)
#define repD(i, a, n)  for(int i = a; i >= (n); --i)
#define trav(a, x) for(auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()
#define fill(a)  memset(a, 0, sizeof (a))
#define fst first
#define snd second
#define mp make_pair
#define pb push_back
typedef long double ld;
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

void pre(){


}
const ll mod=1e9+7;
vi g[100009];
ll odd[100009],even[100009];
int a[100009],n,x;
void dfs(int v,int p){
	even[v] = 1;
	trav(i,g[v]){
		if(i!=p){
			dfs(i,v);
			a[v]^=a[i];
			tie(even[v],odd[v]) = mp((even[v]*even[i]+odd[v]*odd[i])%mod,(odd[v]*even[i]+odd[i]*even[v])%mod);
		}
	}
	if(x==0){
		if(a[v]==0){
			tie(odd[v],even[v]) = mp((odd[v]+even[v])%mod,(odd[v]+even[v])%mod);
		}
	}
	else if(a[v]==x){
		odd[v] = (odd[v]+even[v])%mod;
	}
	else if(a[v]==0){
		even[v] = (odd[v]+even[v])%mod;
	}
}

int main() {
	cin.sync_with_stdio(0); cin.tie(0);
	cin.exceptions(cin.failbit);
	pre();
	cin>>n>>x;
	rep(i,n) cin>>a[i];
	rep(i,n-1){
		int u,v;cin>>u>>v;u--,v--;
		g[u].pb(v);
		g[v].pb(u);
	}
	dfs(0,-1);
	if(a[0]==0) cout<<odd[0];
	else if(a[0]==x) cout<<even[0];
	else cout<<0;
	return 0;
}