#include<bits/stdc++.h>

using namespace std;

const int N=1e5+10;

struct Node{
	int sum;
	int a,b;
} node[N];
int n,t;

bool cmp(Node x,Node y)
{
	return x.sum>y.sum;
}

int main()
{
	cin>>t;
	while(t--)
	{
		scanf("%d",&n);
		for(int i=1;i<=n;i++)
		{
			scanf("%d%d",&node[i].a,&node[i].b);
			node[i].sum=node[i].a+node[i].b;
		} 
		sort(node+1,node+1+n,cmp);
		long long ans=0;
		int flag=1;
		for(int i=n;i>=1;i--)
		{
			if(flag==1)
			{
				ans+=node[i].a;
			}
			else 
			{
				ans-=node[i].b;
			}
			flag*=-1;
		}
		printf("%lld\n",ans);
	}
	return 0;
}