Perfect Sum

/*
    Task    : _example
    Author  : Phumipat C. [MAGCARI]
    Language: C++
    Created : 31 October 2022 [21:53]
*/
#include<bits/stdc++.h>
using namespace std;
map<long long ,int > cnt;
int main(){
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    int q;
    cin >> q;
    while(q--){
        int n;
        long long mx = -1;
        cin >> n;
        for(int i=1;i<=n;i++){
            long long num;
            cin >> num;
            mx = max(mx,num);
            cnt[num]++;
            while(cnt[num] > 1){
                cnt[num] = 0;
                cnt[num+1]++;
                mx = max(mx,num+1);
                num++;
            }
        }
        int sum = 0;
        for(auto x:cnt)
            sum+=x.second;
        cout << mx+1-sum << '\n';
        cnt.clear();
    }
    return 0;
}