#include<bits/stdc++.h>
using namespace std;
#define int long long
inline int read(){
    int s=0,w=1;
    char ch=getchar();
    while(ch>'9'||ch<'0'){
        if(ch=='-')w=-1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9'){
        s=(s<<3)+(s<<1)+ch-'0';
        ch=getchar();
    }
    return s*w;
}
int t,n,ans;
struct tree{
    int v,w;
}tr[1000005];
bool cmp(tree a,tree b){
    if(a.v!=b.v)return a.v<b.v;
    return a.w<b.w;
}

bool check(int x){
    priority_queue<int>q1,q2;
    for(int i=1;i<=n;i++){
        if(tr[i].v>=x)q1.push(tr[i].v+tr[i].w-x);
        else q2.push(tr[i].w);
    }
    if(q1.size()<q2.size())return 0;
    for(int i=1;i<=q2.size();i++){
        int x=q1.top(),y=q2.top();
        q1.pop();q2.pop();
        if(x<y)return 0;
    }
    return 1;
}
signed main(){
    t=read();
    while(t--){
        n=read();
        ans=1;
        for(int i=1;i<=n;i++){
            tr[i].v=read(),tr[i].w=read();
        }
        int l=1,r=1e18;
        while(l<=r){
            int mid=l+r>>1;
            if(check(mid))ans=mid,l=mid+1;
            else r=mid-1;
        }
        cout<<ans<<endl;
    }
}