#include<bits/stdc++.h>
#define fo(s) freopen(s".in","r",stdin),freopen(s".out","w",stdout)
#define Ts template<typename Ty,typename... Ar>
#define Tp template<typename Ty>
#define isdigit(c) ((c)>='0'&&(c)<='9')
#define ll long long
#define RS register
#define gc getchar
#define pc putchar
#define I inline
using namespace std;
Tp I Ty wmax(Ty a,Ty b){return a>=b? a:b;}
Tp I Ty wmin(Ty a,Ty b){return a<=b? a:b;}
namespace WrongIO
{
	Tp I void read(Ty &x){x=0;Ty opt=1;char c=gc();while(!isdigit(c)&&c!='-')c=gc();if(c=='-')opt=-1,c=gc();while(isdigit(c))x=(x<<3)+(x<<1),x+=c-'0',c=gc();x*=opt;return;}
	Tp I void write(Ty x){short OI_USE[50],OI_top=0;if(x<=0) if(x==0)pc('0');else pc('-'),x*=-1;while(x)OI_USE[++OI_top]=x%10,x/=10;while(OI_top--)pc(OI_USE[OI_top+1]+'0');return;}
    I void writec(char c[]){int len=strlen(c);for(int i=0;i<len;i++)pc(c[i]);}
    I void writes(string s){int len=s.length();for(int i=0;i<len;i++)pc(s[i]);}
    I void readc(char &c,int l,int r){c=gc(); while(c!=EOF&&(c<l||c>r)) c=gc();}
    I void readc(char &c,char val){c=gc();while(c!=EOF&&c!=val) c=gc();}
    I void readc(char val){char c;c=gc();while(c!=EOF&&c!=val) c=gc();}
    I void readls(string &s){char c=gc();while(c!='\n') s.push_back(c),c=gc();}
    Ts I void read(Ty &x,Ar &...y) {read(x),read(y...);}
} using namespace WrongIO;
ll n,m;
ll sx[800050],cl[400050];
struct awa{
	ll u,v,lca,id;
}que[5000050];
ll vis[400050],tg[400050],tp;
map<ll,ll> CL;
ll fa[400050],dth[400050],tp2;
ll fst[400050],lst[400050];
ll st[400050][20];
ll St[400050],Ed[400050],bl[400050];
ll num,siz,ans;
vector<ll> vt[400050];
void dfs(ll u)
{
	sx[++tp2]=u;
	fst[u]=tp2;
	for(ll v:vt[u])
	{
		if(v==fa[u]) continue;
		dth[v]=dth[u]+1; fa[v]=u;
		st[v][0]=u; dfs(v);
	}
	sx[++tp2]=u;
	lst[u]=tp2;
	return;
}
ll LCA(ll x,ll y)
{
	if(dth[x]>dth[y]) swap(x,y);
	for(int i=18;i>=0;i--)
	if(dth[st[y][i]]>=dth[x]) y=st[y][i];
	if(x==y) return x;
	for(int i=18;i>=0;i--)
	if(st[x][i]!=st[y][i]) x=st[x][i],y=st[y][i];
	return fa[x];
}
bool cmp(awa x,awa y)
{
	if(bl[x.u]!=bl[y.u]) return x.u<y.u;
	return x.v<y.v;
}
void ad(ll pos)
{
	vis[sx[pos]]^=1;
	if(vis[sx[pos]])
	{
		tg[cl[sx[pos]]]++;
		if(tg[cl[sx[pos]]]==1) ans++;
	}
	else
	{
		tg[cl[sx[pos]]]--;
		if(tg[cl[sx[pos]]]==0) ans--;
	}
}
ll res[5000050];
int main()
{
    read(n,m);
    for(int i=1;i<=n;i++)
    {
    	ll tep; read(tep);
    	if(CL[tep]==0) CL[tep]=++tp;
    	cl[i]=CL[tep];
	}
	for(int i=1;i<n;i++)
	{
		ll u,v; read(u,v);
		vt[u].push_back(v);
		vt[v].push_back(u);
	}
	fa[1]=1; dth[1]=1; st[1][0]=1; dfs(1);
	for(int i=1;i<=n;i++)
	for(int j=1;j<=18;j++)
	st[i][j]=st[st[i][j-1]][j-1];
	for(int i=1;i<=m;i++)
	{
		ll u,v; read(u,v);
		if(fst[u]>fst[v]) swap(u,v);
		que[i].lca=LCA(u,v);
		if(que[i].lca==u)
		{
			que[i].lca=-1;
			que[i].u=fst[u];
			que[i].v=fst[v];
		}
		else que[i].u=lst[u],que[i].v=fst[v];
		que[i].id=i;
	}
	siz=sqrt(m*2/3); num=ceil(n*2.0/siz);
	for(int i=1;i<=num;i++) St[i]=siz*(i-1)+1,Ed[i]=siz*i; Ed[num]=n*2;
	for(int i=1;i<=num;i++)
	for(int j=St[i];j<=Ed[i];j++)
	bl[j]=i;
	sort(que+1,que+m+1,cmp);
	ll L=1,R=0;
	for(int i=1;i<=m;i++)
	{
		if(sx[que[i].u]==sx[que[i].v])
		{
			res[que[i].id]=1;
			continue;
		}
		while(L<que[i].u) 
		ad(L++);
		while(L>que[i].u) 
		ad(--L);
		while(R<que[i].v) 
		ad(++R);
		while(R>que[i].v) 
		ad(R--);
		ll at=0;
		if(que[i].lca!=-1)
		if(tg[cl[que[i].lca]]==0) at=1;
		res[que[i].id]=ans+at;
	}
	for(int i=1;i<=m;i++)
	write(res[i]),pc('\n');
}