#include<bits/stdc++.h>
using namespace std;
#define int long long
struct coin1{
    int timer,pos;
};
int n;
coin1 coin[1000006];
int check(int k){
    pair<int,int> robot[2];
    robot[0].first = 0;
    robot[0].second = 0;
    robot[1].first = 0;
    robot[1].second = 0;
    for (int i = 1;i<=n;i++){
        if (robot[0].first == 0){
            robot[0].second  = coin[i].timer;
            robot[0].first = coin[i].pos;
        }else if ((robot[0].first + (coin[i].timer-robot[0].second)*k >= coin[i].pos) &&  (robot[0].first - (coin[i].timer-robot[0].second)*k <= coin[i].pos)){
            robot[0].first = coin[i].pos;
            robot[0].second = coin[i].timer;
        }else if (robot[1].first==0){
            robot[1].first = coin[i].pos;
            robot[1].second = coin[i].timer;
        }else if ((robot[1].first + (coin[i].timer-robot[1].second)*k)>=coin[i].pos && (robot[1].first - (coin[i].timer-robot[1].second)*k)<=coin[i].pos){
            robot[1].first = coin[i].pos;
            robot[1].second = coin[i].timer;
        }else return 0;
    }

    return 1;
}
bool cmp(coin1 a,coin1 b){
    if (a.timer !=b.timer)
    return a.timer < b.timer;
    else return a.pos < b.pos;
}
signed main(){
    int tc;
    cin >> tc;
    while(tc--){
    cin >> n ;
    for (int i = 1;i<=n;i++){
        cin >> coin[i].timer >> coin[i].pos;
    }
    sort(coin+1,coin+1+n,cmp);

    int l = 0,r = 1e9,res=-1,cnt= 0;
    while(l<=r){
        int mid = (l+r)/2;
        if (check(mid)==1){
            res= mid;
            r = mid-1;
        }else {
            l = mid + 1;
        }
    }
    cout << res << "\n";
    }
    return 0;
}