#include<bits/stdc++.h>
using namespace std;
const int N=5e5+10;
int a[N],t[N],pre[N],ans[N];
int lowbit(int x){
	return x&-x;
}
void add(int j,int x){
	for(int i=j;i<N;i+=lowbit(i)){
		t[i]+=x;
	}
}
int sum(int j){
	int ret=0;
	for(int i=j;i;i-=lowbit(i)){
		ret+=t[i];
	}
	return ret;
}
struct Node{
	int mex;
	int l,r;
	bool operator<(const Node &u)const
	{
		return r<u.r;
	}
};
void solve(){
	int n,m;
	cin >> n >> m;
	for(int i=0;i<=n+10;++i){
		t[i]=0;
		pre[i]=0;
		ans[i]=0;
	}
	vector<Node> v;
	for(int i=1;i<=n;++i) std::cin >> a[i];
	for(int i=1;i<=n;++i){
		if(!pre[a[i]]) {
			pre[a[i]]=i;
			if(i>1){
				v.push_back({a[i],1,i-1});
			}
		}
		else {
			if(i-pre[a[i]]>=2){
				v.push_back({a[i],pre[a[i]]+1,i-1});
			}
			pre[a[i]]=i;
			
		}
	}
	for(int i=1;i<=m+1;++i){
		if(i==a[n]) continue;
		if(!pre[i]){
			v.push_back({i,1,n});
		}else{
			if(n-pre[i]>=2){
				v.push_back({i,pre[i]+1,n});
			}
		}
	}
	sort(v.begin(),v.end());
	/*
	for(auto [mex,l,r]:v){
		cout<<mex<<" "<<l<<" "<<r<<'\n';
	} */
	for(int i=0;i<=m+10;++i) pre[i]=0;
	int lst=1;
	for(auto [mex,l,r]:v){
		for(int i=lst;i<=r;++i){
			if(pre[a[i]]){
				add(pre[a[i]],-1);
				
				
			}
			add(i,1);
			pre[a[i]]=i;
		}
		lst=r+1;
		ans[mex]=max(ans[mex],sum(r)-sum(l-1));
	}
	int ret=-1;
	for(int i=1;i<=m+1;++i){
		ret=std::max(ret,ans[i]-i);
	}
	std::cout<<ret<<"\n";
}
int main(){
	int t;
	cin >> t;
	while(t--){
		solve();
	} 
	return 0;
}