#include<bits/stdc++.h>
#define int long long
#define endl '\n'
const int MAXN=1e5+5;

int T;
int n;
int v[MAXN],w[MAXN];
int a[MAXN],b[MAXN];//a no b yes

bool cmpa(int a,int b){return w[a]>w[b];}
bool cmpb(int a,int b){return (w[a]+v[a])>(w[b]+v[b]);}

bool check(int x){
	memset(a,0,sizeof(a));
	memset(b,0,sizeof(b));
	int cnta=0,cntb=0;
	for(int i=1;i<=n;i++){
		if(v[i]<x)a[++cnta]=i;
		else b[++cntb]=i;
	}
	
	if(cnta>cntb)return false;
	std::sort(a+1,a+cnta+1,cmpa);
	std::sort(b+1,b+cntb+1,cmpb);
	for(int i=1;i<=cnta;i++){
		int now=v[b[i]]-(w[a[i]]-w[b[i]]);
		if(now<x)return false;
	}
	return true;
}

signed main(){
	std::cin>>T;
	while(T--){
		std::cin>>n;
		for(int i=1;i<=n;i++)std::cin>>v[i]>>w[i];
		int l=1,r=1e9;
		while(l<r){
			int mid=(l+r+1)/2;
			if(check(mid))l=mid;
			else r=mid-1;
		}
		std::cout<<l<<endl;
	}
	
	return 0;
}