Code：

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<vector>

#include<cstring>

#define INF 0x3f3f3f3f

using namespace std;

int n,m;

#define MAXN 20010

typedef long long ll;

ll val[MAXN];

struct edge

{

	int to,nxt;

}e[MAXN << 1];

int edgenum = 0;

int lin[MAXN] = {0};

void add(int a,int b)

{

	++edgenum;e[edgenum].to = b;e[edgenum].nxt = lin[a];lin[a] = edgenum;

	++edgenum;e[edgenum].to = a;e[edgenum].nxt = lin[b];lin[b] = edgenum;

	return;

}

#define MAXQ 200010

struct query

{

	int a,b,nxt;

	ll ans;

}q[MAXQ];

int querynum = 0;

int head[MAXN] = {0};

void addq(int a,int b,int lca)

{

	++querynum;q[querynum].a = a;q[querynum].b = b;q[querynum].nxt = head[lca];head[lca] = querynum;

	return;

}

#define MAXB 61

struct linear_base

{

	ll d[MAXB];

	linear_base(){memset(d,0,sizeof(d));}

	void clear(){memset(d,0,sizeof(d));}

	void insert(ll x)

	{

		for(int i = 60;i >= 0;--i)

		{

			if(x & (1ll << i))

			{

				if(d[i] == 0)

				{

					d[i] = x;

					break;

				}

				else x ^= d[i];

			}

		}

		return;

	}

	ll query()

	{

		ll res = 0;

		for(int i = 60;i >= 0;--i)

		{

			if((res ^ d[i]) > res)

			{

				res ^= d[i];

			}

		}

		return res;

	}

}b[MAXN];

linear_base merge(linear_base a,linear_base b)

{

	linear_base res = a;

	for(int i = 0;i <= 60;++i)

	{

		if(b.d[i] != 0)

			res.insert(b.d[i]);

	}

	return res;

}

int s,root;

int size[MAXN],d[MAXN];

bool v[MAXN];

void getroot(int k,int f)

{

	size[k] = 1;d[k] = 0;

	for(int i = lin[k];i != 0;i = e[i].nxt)

	{

		if(v[e[i].to] || e[i].to == f)continue;

		getroot(e[i].to,k);

		size[k] += size[e[i].to];

		if(size[e[i].to] > d[k])

		{

			d[k] = size[e[i].to];

		}

	}

	d[k] = max(d[k],s - d[k]);

	if(d[k] < d[root])root = k;

	return;

}

void getbase(int k,int f,linear_base res)

{

	res.insert(val[k]);

	b[k] = res;

	for(int i = lin[k];i != 0;i = e[i].nxt)

	{

		if(v[e[i].to] || e[i].to == f)continue;

		getbase(e[i].to,k,res);

	}

	return;

}

void calc(int k)

{

	linear_base res;

	getbase(k,0,res);

	linear_base ans;

	for(int i = head[k];i != 0;i = q[i].nxt)

	{

		ans = merge(b[q[i].a],b[q[i].b]);

		q[i].ans = ans.query();

	}

	return;

}

int fa[MAXN];

vector<int> g[MAXN];

void divide(int k)

{

	v[k] = true;

	for(int i = lin[k];i != 0;i = e[i].nxt)

	{

		if(v[e[i].to])continue;

		root = 0;s = size[e[i].to];

		getroot(e[i].to,k);

		fa[root] = k;g[k].push_back(root);

		divide(root);

	}

	return;

}

bool vis[MAXN];

int LCA(int a,int b)

{

	vis[a] = true;

	for(int i = a;fa[i] != 0;i = fa[i])vis[fa[i]] = true;

	int ans;

	if(vis[b])ans = b;

	else for(int i = b;fa[i] != 0;i = fa[i])if(vis[fa[i]]){ans = fa[i];break;}

	vis[a] = false;

	for(int i = a;fa[i] != 0;i = fa[i])vis[fa[i]] = false;

	return ans;

}

void work(int k)

{

	v[k] = true;

	calc(k);

	for(int i = 0;i < g[k].size();++i)

	{

		work(g[k][i]);

	}

	return;

}

int main()

{

	scanf("%d%d",&n,&m);

	for(int i = 1;i <= n;++i)scanf("%lld",&val[i]);

	int a,b; 

	for(int i = 1;i < n;++i)

	{

		scanf("%d%d",&a,&b);

		add(a,b);

	}

	int rt;root = 0;d[0] = INF;s = n;

	getroot(1,0);rt = root;

	divide(root);

	for(int i = 1;i <= m;++i)

	{

		scanf("%d%d",&a,&b);

		addq(a,b,LCA(a,b));

	}

	memset(v,false,sizeof(v));

	work(rt);

	for(int i = 1;i <= m;++i)printf("%lld\n",q[i].ans);

	return 0;

}