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

template<typename T>
using Matrix = vector<vector<T>>;

#define speed ios_base::sync_with_stdio(false); cin.tie(nullptr)
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define nl "\n"
#define ll long long
#define vi vector<int>
#define pi pair<ll,ll> 
#define vpi vector<pair<ll,ll>>
#define vll vector<ll>
#define vb vector<bool>
#define vs vector<string>
#define vc vector<char>
#define vd vector<double>
#define sti stack<int>
#define stll stack<ll>
#define sts stack<string>
#define stc stack<char>
#define qi queue<int>
#define qll queue<ll>
#define qs queue<string>
#define qc queue<char>
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define len size()
#define popcount __builtin_popcountll;
#define forn(i,n) for(ll i=0;i<(n);++i)
#define fori(x,n) for(ll i=x;i<(n);++i)
#define forj(y,m) for(ll j=y;j<(m);++j)
#define rev(a) reverse(a.begin(),a.end())
#define sorta(a) sort(all(a))
#define rall(a) (a).rbegin(),(a).end()
#define sortd(a) sort(rall(a))
#define INF 1e18
#define MOD 1000000007
#define MOD2 998244353
#define PI 3.14159265358979323846
#define fixed(n) fixed << setprecision(n)
#define ceil(n, m) (((n) + (m) - 1) / (m))
#define yesno(b) cout<<(b ? "YES\n" : "NO\n")

signed main() {
    
    speed;
  ll n;
  cin>>n;
  while (n--)
  {
    ll m;
    cin>>m;
    vector<int>arr(m);
    for (ll i = 0; i < m; i++)
    {
cin>>arr[i];
    }

    ll max=-1;
    for (ll i = 0; i < m-1; i++)
    {
        if(arr[i]>=arr[i+1]&&max<arr[i]-arr[i+1]){
max=arr[i]-arr[i+1];
        }
    }
    cout<<max+1<<endl;
  }
  

    
    return 0;
}