造了很多数据都和大佬@HYdroKomide 的题解代码输出一样，但全wa，被自己菜红温了...

#include <iostream>
// #include <bits/stdc++.h>

#define endl '\n'

#define rep(i, a, b) for (int i = a; i <= b; i++)
#define per(i, a, b) for (int i = a; i >= b; i--)

using namespace std;

typedef long long LL;

#define ALL(v) v.begin(), v.end()
#define pb push_back
#define pf push_front
#define qb pop_back
#define qf pop_front
#define eb emplace_back

typedef pair<int, int> pii;
typedef pair<LL, int> pli;

const int dir[4][2] = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}}, inf = 0x3f3f3f3f, mod = 998244353;
const LL infl = 0x3f3f3f3f3f3f3f3fll;

template <class T>
inline bool ckmin(T &x, const T &y) { return x > y ? x = y, 1 : 0; }
template <class T>
inline bool ckmax(T &x, const T &y) { return x < y ? x = y, 1 : 0; }

inline int min(int x, int y) { return x < y ? x : y; }
inline int max(int x, int y) { return x > y ? x : y; }
inline int Abs(int x) { return x > 0 ? x : -x; }
inline void swap(int &x, int &y)
{
	int t = x;
	x = y;
	y = t;
}

int init = []() { /*freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout)*/; return cin.tie(0), cout.tie(0)->sync_with_stdio(0), 0; }();

#include <vector>
const int MAXN = 1e5 + 7;

vector<int> G[MAXN];

int depth[MAXN], parent[MAXN][20], buc[MAXN][20], c[21];

void dfs(int v, int p)
{
	depth[v] = depth[p] + 1;
	parent[v][0] = p;
	buc[v][0] = 1 << c[v] - 1;
	if (p != 0)
		buc[v][0] |= 1 << c[p] - 1;
	for (int i = 1; i <= 19; ++i)
	{
		parent[v][i] = parent[parent[v][i - 1]][i - 1];
		buc[v][i] = (buc[v][i - 1] | buc[parent[v][i - 1]][i - 1]);
	}
	for (int u : G[v])
	{
		if (u != p)
			dfs(u, v);
	}
}
int lca(int u, int v)
{
	int res = 0;
	if (u == v)
	{
		return 1;
	}
	if (depth[u] > depth[v])
		swap(u, v);
	for (int i = 19; i >= 0; --i)
	{
		if (depth[v] - depth[u] >= (1 << i))
		{
			res |= buc[v][i];
			v = parent[v][i];
		}
	}
	if (u == v)
	{
		return res;
	}
	for (int i = 19; i >= 0; --i)
	{
		if (parent[u][i] != parent[v][i] && parent[u][i] != 0 && parent[v][i] != 0)
		{
			res |= buc[u][i], res |= buc[v][i];
			u = parent[u][i], v = parent[v][i];
		}
	}
	res |= (buc[v][0] | buc[u][0]);
	return res;
}
int check(int x)
{
	int ans = 0;
	while (x)
	{
		if (x % 2 == 1)
			ans++;
		x /= 2;
	}
	return ans;
}
int main()
{
	int n, q;
	cin >> n >> q;
	rep(i, 1, n)
	{
		cin >> c[i];
	}
	rep(i, 1, n - 1)
	{
		int u, v;
		cin >> u >> v;
		G[u].pb(v);
		G[v].pb(u);
	}
	dfs(1, 0);
	while (q--)
	{
		int s, t;
		cin >> s >> t;
		cout << check(lca(s, t)) << endl;
	}
	return 0;
}