1607C.cpp

// HHM
// DATE:20-07-2022
#include <bits/stdc++.h>
using namespace std;

#define ll long long int
#define dbl double
#define deb(v) cout << #v << " " << v << "\n"
#define deb2(v, k) cout << #v << " " << v << "\n" \
                        << #k << " " << k << "\n"
#define vin(name, size)        \
    for (i = 0; i < size; i++) \
    cin >> name[i]
#define vout(name)                    \
    for (i = 0; i < name.size(); i++) \
        cout << name[i] << " ";       \
    cout << endl
#define vec(type1, name) vector<type1> name
// #define vp(type1, type2, name) vector<pair<type1, type2>> name
#define st(type, name) set<type> name
#define mpp(type1, type2, name) map<type1, type2> name
#define pb push_back
#define MP make_pair
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define part(x, a, b) x.begin() + a, x.begin() + b
#define Pi 3.1415926535897932384626
ll power(ll a, ll b)
{
    ll res = 1;
    for (ll i = 1; i <= b; i++)
        res *= a;
    return res;
}
// bool comp(pair<ll,char>p1,pair<ll,char>p2){
//     if(p1.F==p2.F)
//         return p1.S<=p2.S;
//     return p1.F<p2.F;
// }
void HHM()
{
    ll i, j, k;
    ll n;cin>>n;
    vector<ll>v;
    for(i=0;i<n;i++){
        ll d;cin>>d;
        v.pb(d);
    }
    sort(all(v));
    ll mx=INT_MIN;
    ll sm=0;
    for(auto x:v){
        mx=max(mx,x-sm);
        sm=x;
    }
    cout<<mx<<"\n";
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    ll t = 1;
   cin >> t;
    // ll tt=1;
    while (t--)
    {
        // cout << "Case #" << tt << ": ";
        HHM();
        // tt++;;
    }
}
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);