#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }


// T: monoid representing information of an interval.
//   T()  should return the identity.
//   T(S s)  should represent a single element of the array.
//   T::pull(const T &l, const T &r)  should pull two intervals.
template <class T> struct SegmentTreePoint {
  int logN, n;
  vector<T> ts;
  SegmentTreePoint() {}
  explicit SegmentTreePoint(int n_) {
    for (logN = 0, n = 1; n < n_; ++logN, n <<= 1) {}
    ts.resize(n << 1);
  }
  template <class S> explicit SegmentTreePoint(const vector<S> &ss) {
    const int n_ = ss.size();
    for (logN = 0, n = 1; n < n_; ++logN, n <<= 1) {}
    ts.resize(n << 1);
    for (int i = 0; i < n_; ++i) at(i) = T(ss[i]);
    build();
  }
  T &at(int i) {
    return ts[n + i];
  }
  void build() {
    for (int u = n; --u; ) pull(u);
  }

  inline void pull(int u) {
    ts[u].pull(ts[u << 1], ts[u << 1 | 1]);
  }

  // Changes the value of point a to s.
  template <class S> void change(int a, const S &s) {
    assert(0 <= a); assert(a < n);
    ts[a += n] = T(s);
    for (; a >>= 1; ) pull(a);
  }

  // Applies T::f(args...) to point a.
  template <class F, class... Args>
  void ch(int a, F f, Args &&... args) {
    assert(0 <= a); assert(a < n);
    (ts[a += n].*f)(args...);
    for (; a >>= 1; ) pull(a);
  }

  // Calculates the product for [a, b).
  T get(int a, int b) {
    assert(0 <= a); assert(a <= b); assert(b <= n);
    if (a == b) return T();
    a += n; b += n;
    T prodL, prodR, t;
    for (int aa = a, bb = b; aa < bb; aa >>= 1, bb >>= 1) {
      if (aa & 1) { t.pull(prodL, ts[aa++]); prodL = t; }
      if (bb & 1) { t.pull(ts[--bb], prodR); prodR = t; }
    }
    t.pull(prodL, prodR);
    return t;
  }

  // Calculates T::f(args...) of a monoid type for [a, b).
  //   op(-, -)  should calculate the product.
  //   e()  should return the identity.
  template <class Op, class E, class F, class... Args>
#if __cplusplus >= 201402L
  auto
#else
  decltype((std::declval<T>().*F())())
#endif
  get(int a, int b, Op op, E e, F f, Args &&... args) {
    assert(0 <= a); assert(a <= b); assert(b <= n);
    if (a == b) return e();
    a += n; b += n;
    auto prodL = e(), prodR = e();
    for (int aa = a, bb = b; aa < bb; aa >>= 1, bb >>= 1) {
      if (aa & 1) prodL = op(prodL, (ts[aa++].*f)(args...));
      if (bb & 1) prodR = op((ts[--bb].*f)(args...), prodR);
    }
    return op(prodL, prodR);
  }

  // Find min b s.t. T::f(args...) returns true,
  // when called for the partition of [a, b) from left to right.
  //   Returns n + 1 if there is no such b.
  template <class F, class... Args>
  int findRight(int a, F f, Args &&... args) {
    assert(0 <= a); assert(a <= n);
    if ((T().*f)(args...)) return a;
    if (a == n) return n + 1;
    a += n;
    for (; ; a >>= 1) if (a & 1) {
      if ((ts[a].*f)(args...)) {
        for (; a < n; ) {
          if (!(ts[a <<= 1].*f)(args...)) ++a;
        }
        return a - n + 1;
      }
      ++a;
      if (!(a & (a - 1))) return n + 1;
    }
  }

  // Find max a s.t. T::f(args...) returns true,
  // when called for the partition of [a, b) from right to left.
  //   Returns -1 if there is no such a.
  template <class F, class... Args>
  int findLeft(int b, F f, Args &&... args) {
    assert(0 <= b); assert(b <= n);
    if ((T().*f)(args...)) return b;
    if (b == 0) return -1;
    b += n;
    for (; ; b >>= 1) if ((b & 1) || b == 2) {
      if ((ts[b - 1].*f)(args...)) {
        for (; b <= n; ) {
          if (!(ts[(b <<= 1) - 1].*f)(args...)) --b;
        }
        return b - n - 1;
      }
      --b;
      if (!(b & (b - 1))) return -1;
    }
  }
};

////////////////////////////////////////////////////////////////////////////////

struct Node {
  bool a[2][2];
  Node() : a{} {
    a[0][0] = a[1][1] = true;
  }
  Node(int f) : a{} {
    if (f & 1) a[0][0] = true;
    if (f & 2) a[0][1] = true;
    if (f & 4) a[1][0] = true;
  }
  void pull(const Node &l, const Node &r) {
    for (int u = 0; u < 2; ++u) for (int v = 0; v < 2; ++v) {
      a[u][v] =
          (l.a[u][0] && r.a[0][v]) || 
          (l.a[u][1] && r.a[1][v]);
    }
  }
};


constexpr Int INF = 1001001001001001001LL;

int N;
vector<Int> A;

int main() {
  for (int numCases; ~scanf("%d", &numCases); ) { for (int caseId = 1; caseId <= numCases; ++caseId) {
    scanf("%d", &N);
    A.resize(N);
    for (int i = 0; i < N; ++i) {
      scanf("%lld", &A[i]);
    }
    
    vector<pair<Int, int>> es(2 * N - 1);
    for (int i = 0; i < N; ++i) {
      es[i + i] = make_pair(A[i], i + i);
      if (i + 1 < N) {
        es[i + (i + 1)] = make_pair(A[i] + A[i + 1], i + (i + 1));
      }
    }
    sort(es.begin(), es.end());
// cerr<<"es = "<<es<<endl;
    
    vector<int> fs(N, 0);
    SegmentTreePoint<Node> seg(fs);
    Int ans = INF;
    for (int l = 0, r = 0; l < 2 * N - 1; ++l) {
      for (; r < 2 * N - 1 && !seg.ts[1].a[0][0]; ++r) {
        const int j = es[r].second;
        const int i = j / 2;
        if (j & 1) {
          seg.change(i, fs[i] ^= 2);
          seg.change(i + 1, fs[i + 1] ^= 4);
        } else {
          seg.change(i, fs[i] ^= 1);
        }
      }
#ifdef LOCAL
int brt;
for(brt=l+1;brt<=2*N-1;++brt){
 vector<vector<int>>graph(N);
 for(int h=l;h<brt;++h){
  const int j=es[h].second;
  graph[j/2].push_back(j/2+1+(es[h].second&1));
 }
 vector<int>dp(N+1,0);
 dp[0]=1;
 for(int i=0;i<N;++i)if(dp[i])for(const int ii:graph[i])dp[ii]=1;
 if(dp[N])break;
}
if(brt!=(seg.ts[1].a[0][0]?r:2*N)){
 cerr<<"HELP "<<l<<" "<<r<<"; brt = "<<brt<<endl;
 cerr<<"  fs = "<<fs<<endl;
 assert(false);
}
#endif
      if (seg.ts[1].a[0][0]) {
// cerr<<"OK "<<l<<" "<<r<<endl;
        chmin(ans, es[r - 1].first - es[l].first);
      }
      {
        const int j = es[l].second;
        const int i = j / 2;
        if (j & 1) {
          seg.change(i, fs[i] ^= 2);
          seg.change(i + 1, fs[i + 1] ^= 4);
        } else {
          seg.change(i, fs[i] ^= 1);
        }
      }
    }
    printf("%lld\n", ans);
  }
#ifndef LOCAL
  break;
#endif
  }
  return 0;
}