# include <bits/stdc++.h>
using namespace std;
const int N = 5e5 + 5; 
int n, m; 
int a[N], b[N], L; 
int pre[N]; 
struct node
{
	int l, Mex; 
}; 
vector <node> Seg[N]; 
struct BIT
{
	int c[N]; 
	int lowbit(int x) { return x & (-x); }
	void clear(void) {for(int i = 0; i <= n + 1; i++) c[i] = 0; return; }
	void add(int x, int d = 1)
	{
		while(x <= n + 1) c[x] += d, x += lowbit(x); 
		return; 
	}
	int query(int x) 
	{
		int ans = 0; 
		while(x) ans += c[x], x -= lowbit(x); return ans;
	}
	void update(int l, int r) {add(l, 1), add(r + 1, -1); return; }
}T;
int main(void)
{
	int Test; scanf("%d", &Test);
	while(Test--)
	{
		scanf("%d%d", &n, &m); 
		L = 0; 
		for(int i = 1; i <= n; i++) scanf("%d", &a[i]), b[++L] = a[i], b[++L] = a[i] + 1; 
		sort(b + 1, b + L + 1); L = unique(b + 1, b + L + 1) - b - 1; 
		for(int i = 1; i <= L; i++) pre[i] = 0;
		for(int i = 1; i <= n; i++) Seg[i].clear(); 
		for(int i = 1; i <= n; i++)
		{
			a[i] = lower_bound(b + 1, b + L + 1, a[i]) - b; 
			if(!pre[a[i]] && 1 <= i - 1) Seg[i - 1].push_back({1, a[i]}); 
			else if(pre[a[i]] + 1 <= i - 1) Seg[i - 1].push_back({pre[a[i]] + 1, a[i]});
			pre[a[i]] = i; 
		}
		for(int i = 1; i <= L; i++)
		{
			if(pre[i] + 1 <= n) Seg[n].push_back({pre[i] + 1, i});
		}
		for(int i = 1; i <= L; i++) pre[i] = 0; 
		T.clear();
		int ans = -1e9; 
		for(int r = 1; r <= n; r++)
		{	
			T.update(pre[a[r]] + 1, r); pre[a[r]] = r; 
			for(auto I : Seg[r])
			{
				ans = max(ans, T.query(I.l) - b[I.Mex]);
			}
		}	
		printf("%d\n", ans);
	}
	return 0; 
}