#include<bits/stdc++.h>
using namespace std;
#define ll long long
int main(){
    ll t;
    cin >> t;
    while (t--)
    {
        ll n;
        cin >> n;
        vector<ll> a(n);
        for(ll i=0;i<n;i++)cin>>a[i];
        sort(a.begin(),a.end(),greater<ll>());
        ll sum = 0;
        for(ll i=0;i<n;i++){
            if(i>=2 && a[i]<=0)break;
            if(i%2==0)sum+=a[i];
            else sum-=a[i];
        }
        cout << sum << endl;
    }
}