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

#define f first
#define s second
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(v) v.begin(), v.end()
#define sz(v) (int)v.size()
#define sq(a) ((a)*(a))

#define MOO(i,a,b) for (int i=a; i<b; i++)
#define M00(i,a) for (int i=0; i<a; i++)
#define MOOd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define M00d(i,a) for (int i = (a)-1; i >= 0; i--)

#define per(i,a,b) for (int i = (b)-1; i >= a; i--)
#define rep(i,a,b) for (int i=a; i<b; i++)

#define FOR(i,a,b) for (int i=a; i<b; i++)
#define F0R(i,a) for (int i=0; i<a; i++)
#define ROF(i,a,b) for (int i = (b)-1; i >= a; i--)
#define R0F(i,a) for (int i = (a)-1; i >= 0; i--)

#define FAST ios::sync_with_stdio(0); cin.tie(0);
#define finish(x) return cout << x << endl, 0;
#define dbg(x) cout << ">>> " << #x << " = " << x << endl;
#define _<< " _ " <<

#define int long long

template<class T> bool ckmin(T&a, T&b) { bool B = a > b; a = min(a,b); return B; }
template<class T> bool ckmax(T&a, T&b) { bool B = a < b; a = max(a,b); return B; }

typedef long double ld;
typedef pair<int,int> pi;
typedef pair<ld,ld> pld;
typedef complex<ld> cd;

typedef vector<int> vi;
typedef vector<ld> vld;
typedef vector<vector<int>> vvi;

const ld PI = acos(-1.0);
const ld EPS = 1e-7;
const int MOD = 1e9+7;

int POW(int b, int e) {
	int r = 1;
	while(e) {
		if(e % 2 == 1) {
			r *= b;
			r %= MOD;
		}
		e /= 2;
		b *= b;
		b %= MOD;
	}
	return r;
}
int gcd(int a, int b) {
	if(b > a) return gcd(b,a);
	if(b == 0) return a;
	return gcd(b, a % b);
}
int INV(int a) {
	return POW(a, MOD-2);
}
//Constants and Variables here
struct Tree {
	typedef int T;
	T unit = 9;
	
	T f(T &a, T &b) { 
	    //return a;
	    
		int res = 0;
		
		M00(i, 2) M00(j, 2) { 
			M00(k, 2) {
				res |= ((b >> (2 * i + k)) & (a >> (2 * k + j)) & 1) << (2 * i + j);
			}
		}
		
		//if (a == 4 && b == 4)
		//    dbg(a _ b _ res);
		
		return res;
	}
	vector<T> s; int n;
	Tree(int n, T def) : s(2*n, def), n(n) {
	    for(int i = n - 1; i >= 0; i --){
	        s[i] = f(s[2 * i], s[2 * i + 1]);
	    }
	}
	void update(int pos, int i, int j, int val) {
	    pos += n;
	    
	    int mask = 1 << (2 * i + j);
	    
	    if (val){
	        s[pos] |= mask;
	    } else {
	        //dbg(s[pos] _ pos _ i _ j);
	        s[pos] &= ~mask;
	        //dbg(s[pos]);
	    }
	    
	    
	    
		for (; pos /= 2;)
			s[pos] = f(s[pos * 2], s[pos * 2 + 1]);
	}
	T query(int b, int e) { // query [b, e)
		T ra = unit, rb = unit;
		for (b += n, e += n; b < e; b /= 2, e /= 2) {
			if (b % 2) ra = f(ra, s[b++]);
			if (e % 2) rb = f(s[--e], rb);
		}
		return f(ra, rb);
	}

	T access(int u) {
		return s[u + n];
	}
};
Tree T(0, 0);
vector<pair<int, pi>> dom;

void add(int x) {
	pi p = dom[x].s;
	if(p.f == p.s) {
		T.update(p.f, 0, 0, 1);
	} else {
		T.update(p.s, 0, 1, 1);
	}
}

void rem(int x) {
	pi p = dom[x].s;
	if(p.f == p.s) {
		T.update(p.f, 0, 0, 0);
	} else {
		T.update(p.s, 0, 1, 0);
	}
}

void solve() {
	int n; cin >> n;
	vi arr(n);
	M00(i, n){
	    //arr[i] = rand();
	    cin >> arr[i];
	}

	dom.clear();	
	M00(i, n) dom.pb(mp(arr[i], mp(i,i)));
	M00(i, n-1) dom.pb(mp(arr[i]+arr[i+1], mp(i,i+1)));
	
	sort(all(dom));
	
	M00(i, 2 * n - 1){
	    //cout << dom[i].s.f _ dom[i].s.s << endl;
	}

	int base = 4;
	T = Tree(n, base);

	int ans = 1e10;
	int r = -1, l = 0; // closed
	while(l < dom.size()) {
		while( (!(T.query(0, n) & 1)) && r < (int) dom.size()) {
			r += 1;
			if (r == dom.size()) break;
			add(r);
		}

		if (r == dom.size()) break;


		//dbg(T.query(0, 1) _ l _ r);
		//dbg(T.query(0, 2) _ l _ r);
		//dbg(T.query(0, 3) _ l _ r);
		//dbg(T.query(0, 4) _ l _ r);

		ans = min(ans, dom[r].f - dom[l].f);
		
		if(l == dom.size() - 1) break;
		
        rem(l);
		l++;
	}
	cout << ans << endl;
}

int32_t main() { FAST
	mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
	int t; cin >> t;
	while(t--) solve();
}