#include<cstdio>
#include<algorithm>
using namespace std;
#define ll long long
const int Max = 1e6 + 50;
ll n,t;
ll Abs(ll a){
return a < 0 ? -a : a;
}
ll min(ll a,ll b){
return a < b ? a : b;
}
ll max(ll a,ll b){
return a > b ? a : b;
}
struct Node{
ll a;
ll b;
}node[Max];
bool cmp(Node x,Node y){
return min(x.a,y.b) < min(y.a,x.b);
}
int main(){
scanf("%lld",&t);
ll i,c,maxc;
ll sum;
while(t--){
scanf("%lld",&n);
for(i = 1;i <= n;++i){
scanf("%lld %lld",&node[i].a,&node[i].b);
}
sort(node+1,node+n+1,cmp);
c = node[1].a + node[1].b;
sum = node[1].a;
maxc = c;
for(i = 2;i <= n;++i){
sum += node[i].a;
c = max(c,sum) + node[i].b;
maxc = max(maxc,c);
}
printf("%lld\n",maxc);
}
return 0;
}
WA了最后4个点 写了好久都没过