#ifdef DEBUG
//#define _GLIBCXX_DEBUG
#endif
//#pragma GCC optimize("O3")
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;

const ll mod = 1000000007;
//const ll mod = 998244353;

#define X first
#define Y second

ll pew(ll a, ll b)
{
    ll res = 1;
    while (b>0)
    {
        if (b&1) res = res*a%mod;
        b >>= 1;
        a = a*a%mod;
    }
    return res;
}



void solve()
{
    ll n;
    cin >> n;
    vector<ll> a(n);
    ll A = 0;
    for (ll i=0;i<n;i++)
    {
        ll x, y;
        cin >> x >> y;
        A += x;
        a[i] = y+x;
    }
    sort(a.begin(),a.end());
    reverse(a.begin(),a.end());
    for (ll i=1;i<n;i+=2)
    {
        A -= a[i];
    }
    cout << A << "\n";
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
//#ifdef DEBUG
    //freopen("input.txt", "r", stdin);
//#endif
    int T = 1;
    cin >> T;
    while (T--) solve();
    return 0;
}