RT，1-7WA，8TLE，9-10RE

#include<bits/stdc++.h>
using namespace std;

const int MAX=4e4+100;
const int N=5e2+1;

struct edge{
	int to,net;
}ed[MAX<<1],edCT[MAX<<1];

int hed[MAX],cnt;
int hedCT[MAX],cntCT;
int val[MAX];

void add(int x,int y){
	ed[++cnt].net=hed[x];
	hed[x]=cnt;
	ed[cnt].to=y;
}

void addCT(int x,int y){
	edCT[++cntCT].net=hedCT[x];
	hedCT[x]=cntCT;
	edCT[cntCT].to=y;
}

struct Top_Cluster{
	//BP:界点  CL:簇  CLP:簇路径  CT:收缩树 
	int fa[MAX],B,id[MAX],all;
	int faCT[MAX],dep[MAX],depCT[MAX],belong[MAX];
	int CLP_near[MAX],BP_up[MAX],BP_down[MAX];
	vector<int>BP,downP[MAX];
	
	bitset<MAX>app[N];
	
	int tmp_CL[MAX],tmp_cnt;
	void add_CL(int u,int d) { // u:up v:down
		if(!d) d=tmp_CL[tmp_cnt];
		BP.emplace_back(d);
		CLP_near[u]=u; 
		addCT(u,d);addCT(d,u);
		for(int p=d;p!=u;p=fa[p]) CLP_near[p]=p;
		for(int i=1;i<=tmp_cnt;i++){
			int p=tmp_CL[i],ne;
			BP_up[p]=u;BP_down[p]=d;
			downP[d].emplace_back(p);
			for(ne=p;!CLP_near[ne];ne=fa[ne]);
			CLP_near[p]=CLP_near[ne];
		}
		tmp_cnt=0;
	}
	
	int stk[MAX],top,top_node[MAX];
	int waiting[MAX],BP_rec[MAX];
	void CL_part(int u,int mf){
		fa[u]=mf;
		dep[u]=dep[mf]+1;
		stk[++top]=u;
		top_node[u]=top;
		if(u!=1) waiting[u]=1;
		int BN_cnt=0;
		for(int i=hed[u];i;i=ed[i].net){
			int v=ed[i].to;
			if(v==mf) continue;
			CL_part(v,u);
			waiting[u]+=waiting[v];
			BP_rec[u]=(BP_rec[v]?BN_cnt++,BP_rec[v]:BP_rec[u]);
		}
		if(waiting[u]>B||BN_cnt>1||!mf){
			waiting[u]=0;BP_rec[u]=u;
			int cnt=0,tmp_down=0,j=top_node[u]+1;
			for(int i=hed[u];i;i=ed[i].net){
				int v=ed[i].to;
				if(v==mf) continue;
				if(cnt+waiting[v]>B||(tmp_down&&BP_rec[v])){
					for(;j<top_node[v];j++) tmp_CL[++tmp_cnt]=stk[j];
					add_CL(u,tmp_down);cnt=0;
					tmp_down=0;
				}
				cnt+=waiting[v];
				tmp_down=BP_rec[v]?BP_rec[v]:tmp_down; 
			}
			for(;j<=top;j++) tmp_CL[++tmp_cnt]=stk[j];
			add_CL(u,tmp_down);
			top=top_node[u];
		}
	}
	
	void dfs(int now,int mf){
		faCT[now]=mf;
		depCT[now]=depCT[mf]+1;
		id[now]=++all;
		for(int i=hedCT[now];i;i=edCT[i].net){
			int to=edCT[i].to;
			if(to==mf) continue;
			dfs(to,now);
			app[id[to]][val[now]]=1;
			for(int p=to;p!=now;p=fa[p])
			app[id[to]][val[p]]=1;
//			cout<<to<<" "<<app[id[to]].count()<<"\n"; 
		}
	}
	
	bitset<MAX> get(int x,int y){
		bitset<MAX>res;
		if(dep[x]<dep[y]) swap(x,y);
		while(dep[x]>dep[y]){
			res[val[x]]=1;
			x=fa[x];
		}
		res[val[y]]=1;
		res[val[x]]=1;
		if(x==y) return res;
		while(x!=y) {
			x=fa[x];y=fa[y];
			res[val[x]]=1;
			res[val[y]]=1;
		}
		return res;
	}
	
	int query(int x,int y){
		bitset<MAX>res;
		int u=BP_down[x],v=BP_down[y];
		if(u==v) return get(x,y).count();
		if(depCT[u]<depCT[v]) swap(u,v),swap(x,y);
		res|=get(faCT[u],x);u=faCT[u];
		while(depCT[u]>depCT[v]) res|=app[id[u]],u=faCT[u];
		if(u!=v){
			res|=get(faCT[v],y)|app[id[u]];
			v=faCT[v];u=faCT[u];
			while(u!=v){
				res|=app[id[u]]|app[id[v]];
				u=faCT[u],v=faCT[v];
			}
			return res.count();
		}
		return (res|get(u,y)).count();
	}
}TC;

int n,m;
int tot,g[MAX];

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	
	cin>>n>>m;
	for(int i=1;i<=n;i++) {
		cin>>val[i];
		g[++tot]=val[i];
	}
	for(int i=1;i<n;i++) {
		int x,y;
		cin>>x>>y;
		add(x,y);add(y,x);
	}
	
	sort(g+1,g+tot+1);
	tot=unique(g+1,g+tot+1)-g-1;
	for(int i=1;i<=n;i++){
		val[i]=lower_bound(g+1,g+tot+1,val[i])-g;
	}
	TC.B=sqrt(n);
	TC.BP.emplace_back(1);TC.CL_part(1,0);
	TC.dfs(1,0);
//	for(auto rt1:TC.BP) cout<<rt1<<" ";cout<<"\n";
	
//	cout<<TC.all<<"\n";
	
	int lastans=0;
	for(int i=1;i<=m;i++){
		int u,v;
		cin>>u>>v;
		u=u^lastans;
		cout<<(lastans=TC.query(u,v))<<"\n";
	}
	
	return 0;
}