#include<bits/stdc++.h>
using namespace std;
#define int long long
#define PII pair<int,int>
#define lson 2*p
#define rson 2*p+1
#define x first
#define y second
//#define endl "\n"
constexpr int N=1e6+10;
constexpr int mod=998244353;
int b[N],a[N];
struct node {
    int a,b;
} f[N];
bool cmp(node a,node b) {
    return a.a+a.b>b.a+b.b;
}
void solve() {
    int n;
    cin>>n;
    for(int i=1;i<=n;i++) cin>>f[i].a>>f[i].b;
    sort(f+1,f+n+1,cmp);
    int ans=0;
    for(int i=1;i<=n;i++) {
        if(i&1) ans+=f[i].a;
        else ans-=f[i].b;
    }
    cout<<ans<<endl;
}
signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int T=1;
    cin>>T;
    while(T--) {
        solve();
    }
}