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

const int N = 1e6 + 10;
int n, m, a[N];
vector<int> g[N];

struct interval_weights
{
	int root[N], tot, last[N];
	struct Node
	{
		int l, r;
		int cnt;
	} tr[N * 40];
	int build(int l, int r)
	{
		int p = ++tot;
		if (l == r) return p;
		int mid = (l + r) >> 1;
		tr[p].l = build(l, mid), tr[p].r = build(mid + 1, r);
		return p;
	}
	int insert(int p, int idx, int l, int r, int x)
	{
		int q = ++tot;
		tr[q] = tr[p], tr[q].cnt += x;
		if (l < r)
		{
			int mid = (l + r) >> 1;
			if (idx <= mid) tr[q].l = insert(tr[p].l, idx, l, mid, x);
			else tr[q].r = insert(tr[p].r, idx, mid + 1, r, x);
		}
		return q;
	}
	int query(int idx, int q, int l, int r)
	{
		if (l == r) return tr[q].cnt;
		int mid = (l + r) >> 1;
		if (idx <= mid) return query(idx, tr[q].l, l, mid) + tr[tr[q].r].cnt;
		else return query(idx, tr[q].r, mid + 1, r);
	}
	int ask(int l, int r)
	{
		return query(l, s.root[r], 1, n);
	}
	void init(int n)
	{
		root[0] = build(1, n);
		for (int i = 1; i <= n; i++)
		{
			if (!last[a[i]]) // 该数据第一次出现
				root[i] = insert(root[i - 1], i, 1, n, 1);
			else
			{
				int t = insert(root[i - 1], last[a[i]], 1, n, -1);
				root[i] = insert(t, i, 1, n, 1);
			}
			last[a[i]] = i;
		}
	}
	void clear(int n)
	{
		for (int i = 1; i <= n; i++) 
		{
			root[i] = 0;
			last[a[i]] = 0;
		}
		for (int i = 0; i <= tot; i++) tr[i] = {0, 0, 0};
		tot = 0;
	}
}s;

void solve()
{
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
	{
		cin >> a[i];
		g[a[i]].push_back(i);
	}
	s.init(n);
	int ans = -1;
	for (int i = 1; i <= min(n + 1, m); i++)
	{
		g[i].push_back(0);
		g[i].push_back(n + 1);
		sort(g[i].begin(), g[i].end());

		for (int j = 1; j < (int)g[i].size(); j++)
		{
			int l = g[i][j - 1] + 1, r = g[i][j] - 1;
			if (l > r) continue;
			ans = max(ans, s.ask(l, r) - i);
		}
		g[i].clear();
	}
	s.clear(n);
	cout << ans << '\n';
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);
	int T; cin >> T;
	while (T--) solve();
	return 0;
}

answer.code: In member function ‘int interval_weights::ask(int, int)’:
answer.code:45:33: error: ‘s’ was not declared in this scope
   45 |                 return query(l, s.root[r], 1, n);
      |                                 ^