#define IOS ios_base::sync_with_stdio(0); cin.tie(0);

 #include <cstdio>//sprintf islower isupper

 #include <cstdlib>//malloc  exit strcat itoa system("cls")

 #include <iostream>//pair

 #include <fstream>

 #include <bitset>

 //#include <map>

 //#include<unordered_map>

 #include <vector>

 #include <stack>

 #include <set>

 #include <string.h>//strstr substr

 #include <string>

 #include <time.h>//srand(((unsigned)time(NULL))); Seed n=rand()%10 - 0~9;

 #include <cmath>

 #include <deque>

 #include <queue>//priority_queue<int, vector<int>, greater<int> > q;//less

 #include <vector>//emplace_back

 //#include <math.h>

 //#include <windows.h>//reverse(a,a+len);// ~ ! ~ ! floor

 #include <algorithm>//sort + unique : sz=unique(b+1,b+n+1)-(b+1);+nth_element(first, nth, last, compare)

 using namespace std;//next_permutation(a+1,a+1+n);//prev_permutation

 #define fo(a,b,c) for(register int a=b;a<=c;++a)

 #define fr(a,b,c) for(register int a=b;a>=c;--a)

 #define mem(a,b) memset(a,b,sizeof(a))

 #define pr printf

 #define sc scanf

 #define ls rt<<1

 #define rs rt<<1|1

 void swapp(int &a,int &b);

 double fabss(double a);

 int maxx(int a,int b);

 int minn(int a,int b);

 int Del_bit_1(int n);

 int lowbit(int n);

 int abss(int a);

 //const long long INF=(1LL<<60);

 const double E=2.718281828;

 const double PI=acos(-1.0);

 const int inf=(<<);

 const double ESP=1e-;

 const int mod=(int)1e9+;

 const int N=(int)1e6+;

 struct node

 {

     long long a,b;

     long long mi;

     friend bool operator<(node a,node b)

     {

         return a.mi<b.mi;

     }

 }P[N];

 int main()

 {

 //    freopen("D:\\QQ DATA\\1659826587\\FileRecv\\hdu-multi2019-8 5个账号 - 复件\\data\\k.in","r",stdin);

     int T;

     sc("%d",&T);

     while(T--)

     {

         int n;

         sc("%d",&n);

         fo(i,,n)

         {

             sc("%lld%lld",&P[i].a,&P[i].b);

             P[i].mi=min(P[i].a,P[i].b);

         }

         sort(P+,P++n);

         long long ans=;

         int pos=n;

         for(int i=n-;i>=;--i)

         {

             long long temp=min(P[i].mi,P[pos].mi);

             ans+=temp*;

             P[i].mi-=temp;P[i].a-=temp;P[i].b-=temp;

             P[pos].mi-=temp;P[pos].a-=temp;P[pos].b-=temp;

             if(P[i].mi)

                 pos=i;

         }

         sort(P+,P++n);

         struct node temp=P[n];

         long long x=,y=;

         for(int i=;i<=n-;++i)

             x+=P[i].a,y+=P[i].b;

         if(x&&temp.b)

         {

             long long tt=min(x,temp.b);

             ans+=tt;

             x-=tt;temp.b-=tt;

         }

         if(y&&temp.a)

         {

             long long tt=min(y,temp.a);

             ans+=tt;

             y-=tt;temp.a-=tt;

         }

         long long xx=min(x,y);

         ans+=xx;

         x-=xx;y-=xx;

         pr("%lld\n",ans);

     }

 //    fclose(stdin);

     return ;

 }

 /**************************************************************************************/

 int maxx(int a,int b)

 {

     return a>b?a:b;

 }

 void swapp(int &a,int &b)

 {

     a^=b^=a^=b;

 }

 int lowbit(int n)

 {

     return n&(-n);

 }

 int Del_bit_1(int n)

 {

     return n&(n-);

 }

 int abss(int a)

 {

     return a>?a:-a;

 }

 double fabss(double a)

 {

     return a>?a:-a;

 }

 int minn(int a,int b)

 {

     return a<b?a:b;

 }