#include <atcoder/all>
using namespace atcoder;
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep2(i,a,b) for (int i = (int)(a); i <= (int)(b); i++)
#define all(v) v.begin(),v.end()
#define inc(x,l,r) ((l)<=(x)&&(x)<(r)) 
#define Unique(x) sort(all(x)), x.erase(unique(all(x)), x.end())
typedef long long ll;
#define int ll
using ld = long double;
using vi = vector<int>;
using vs = vector<string>;
using P = pair<int,int>;
using vp = vector<P>;
template<typename T> using priority_queue_greater = priority_queue<T, vector<T>, greater<T>>;
template<typename T> ostream &operator<<(ostream &os,const vector<T> &v){rep(i,v.size())os<<v[i]<<(i+1!=v.size()?" ":"");return os;}
template<typename T> istream &operator>>(istream& is,vector<T> &v){for(T &in:v)is>>in;return is;}
template<class... T> void in(T&... a){(cin>> ... >> a);}
template<class T> void out(T& a){cout <<a<< '\n';}
template<class T,class... Ts> void out(const T&a, const Ts&... b){cout<< a;(cout<<...<<(cout<<' ',b));cout<<'\n';}
#define INT(...) int __VA_ARGS__; in(__VA_ARGS__)
#define STR(...) string __VA_ARGS__; in(__VA_ARGS__)
#define pcnt __builtin_popcount
int ceil(int x,int y){return x/y+!!(x%y);}
bool ins(string s,string t){return s.find(t)!=string::npos;}
P operator+ (const P &p, const P &q){ return P{p.first+q.first,p.second+q.second};}
P operator- (const P &p, const P &q){ return P{p.first-q.first,p.second-q.second};}
ostream &operator<< (ostream &os, const P &p){os << p.first <<" "<<p.second;return os;}
ostream &operator<< (ostream &os, const modint1000000007 &m){os << m.val();return os;}
ostream &operator<< (ostream &os, const modint998244353 &m){os << m.val();return os;}
template<typename T> bool chmax(T &a, const T b) {if (a < b) {a = b; return true;} else return false; }
template<typename T> bool chmin(T &a, const T b) {if (a > b) {a = b; return true;} else return false; }
void yesno(bool ok){ cout<<(ok?"Yes":"No")<<endl;}
vector<P> dxdy{{1,0},{0,1},{-1,0},{0,-1}};
const int INF = 1e18;
//using mint = modint1000000007;
//using mint = modint998244353;

void solve(){
    INT(n);
    vi a(n);
    cin>>a;
    int ans = 0;
    sort(all(a),greater());
    rep(i,n)ans+=(i&1?-a[i]:a[i]);
    if(n&1)chmax(ans,a[n/2]);
    cout<<ans<<endl;
}
signed main() {
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);

    INT(t);
    while(t--)solve();

    return 0;
}