#include<bits/stdc++.h>
using namespace std;
struct node
{
	int l,r;
	int c[2][2];//l-1+d~r-d connected
	node *lson,*rson;
}*root,pool[233333];
int top;
node *build(int l,int r)
{
	node *tmp=&pool[top++];
	tmp->l=l;tmp->r=r;
	tmp->c[0][0]=tmp->c[0][1]=tmp->c[1][0]=tmp->c[1][1]=0;
	if(l==r)tmp->c[0][1]=tmp->c[1][0]=1;
	if(l==r-1)tmp->c[1][1]=1;
	tmp->lson=tmp->rson=nullptr;
	if(l!=r)
	{
		int mid=(l+r)/2;
		tmp->lson=build(l,mid);
		tmp->rson=build(mid+1,r);
	}
	return tmp;
}
vector<vector<int>> E;
void upd(node *cur,int pos)
{
	cur->c[0][0]=cur->c[0][1]=cur->c[1][0]=cur->c[1][1]=0;
	if(cur->l==cur->r)cur->c[0][1]=cur->c[1][0]=1;
	if(cur->l==cur->r-1)cur->c[1][1]=1;
	if(cur->l==cur->r)
	{
		if(E[cur->l-1][1])
			cur->c[0][0]=1;
		else
			cur->c[0][0]=0;
		return;
	}
	if(cur->l+1==cur->r)
	{
		if(E[cur->l-1][2])
			cur->c[0][0]=1;
		else
			cur->c[0][0]=0;
	}
	if(pos<=cur->lson->r)
		upd(cur->lson,pos);
	else
		upd(cur->rson,pos);
	for(int i=0;i<=1;i++)
	{
		for(int j=0;j<=1;j++)
		{
			cur->c[i][j]|=(cur->lson->c[i][0] and cur->rson->c[0][j] and E[cur->lson->r][1]);
			cur->c[i][j]|=(cur->lson->c[i][1] and cur->rson->c[0][j] and E[cur->lson->r-1][2]);
			cur->c[i][j]|=(cur->lson->c[i][0] and cur->rson->c[1][j] and E[cur->lson->r][2]);
		}
	}
}
int query(node *cur){return cur->c[0][0];}
int main()
{
	ios_base::sync_with_stdio(false);
	int T;
	cin>>T;
	while(T--)
	{
		int n;
		cin>>n;
		vector<int> a(n+5);
		vector<vector<int>> _(n+5,vector<int>(5));
		E.swap(_);
		top=0;
		root=build(1,n);
		for(int i=1;i<=n;i++)
		{
			cin>>a[i];
		}
		vector<tuple<long long,int,int>> edges;
		for(int i=1;i<=n;i++)
		{
			edges.emplace_back(a[i],i-1,i);
			if(i!=n)edges.emplace_back(a[i]+a[i+1],i-1,i+1);
		}
		sort(edges.begin(),edges.end());
		int r=-1;
		long long ans=4e9;
		for(int l=0;l<n+n-1;l++)
		{
			while(r<n+n-2 and not query(root))
			{
				r++;
				auto [w,u,v]=edges[r];
				E[u][v-u]=1;
//				cerr<<"add edge "<<u<<' '<<v-u<<' '<<w<<endl;
				upd(root,u);
				if(v-u==2)upd(root,u+1);
			}
			if(query(root))
			{
//				cerr<<"good "<<l<<' '<<r<<' '<<get<0>(edges[r])-get<0>(edges[l])<<endl;
				ans=min(ans,get<0>(edges[r])-get<0>(edges[l]));
			}
			auto [w,u,v]=edges[l];
			E[u][v-u]=0;
//			cerr<<"del edge "<<u<<' '<<v-u<<' '<<w<<endl;
			upd(root,u);
			if(v-u==2)upd(root,u+1);
		}
		cout<<ans<<"\n";
	}
	
	return 0;
}