#include<bits/stdc++.h>
#define irep(i,l,r) for(int i = l; i <= r; ++i)
#define drep(i,r,l) for(int i = r; i >= l; --i)
#define ceil(pp,qq) (((pp)>0)^((qq)>0)?-Abs(pp)/Abs(qq):(pp)%(qq)?(pp)/(qq)+1:(pp)/(qq))
#define floor(pp,qq) (((pp)>0)^((qq)>0)?-ceil(abs(pp),abs(qq)):(pp)/(qq))
#define ll long long
using namespace std;
ll Abs(ll x){return x > 0 ? x : - x;}
inline ll read(){
	char ch = getchar();
	ll s = 0; bool w = 0;
	while(!isdigit(ch)){if(ch == '-')w = 1;ch = getchar();}
	while(isdigit(ch))s = (s << 3) + (s << 1) + (ch ^ 48), ch = getchar();
	return w ? - s : s;
}

const int itinf = 2e9;
const ll llinf = 4e18;
const int mod = 1000000007;
const int N = 500009;

int main(){
	int T = read();
	while(T --){
		int n = read();
		ll pre = 0;
		vector<ll>a(n);
		irep(i,0,n-1){
			int u = read(), v = read();
			pre -= v;
			a[i] = u + v;
		}
		sort(a.begin(), a.end());
		for(int i = n - 1; i >= 0; i -= 2)pre += a[i];
		printf("%lld\n", pre);
	}
	return 0;
}