#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 = -1e18;
    robot[0].second = 1e18; 

    for (int i = 1; i <= n; i++) {
        int t = coin[i].timer, c = coin[i].pos;
        
        int l = c - (t - coin[i-1].timer) * k;
        int r = c + (t - coin[i-1].timer) * k;

       
        robot[0].first = max(robot[0].first, l);
        robot[0].second = min(robot[0].second, r);

 
        if (robot[0].first > robot[0].second) {
            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;

        while (l <= r) {
            int mid = (l + r) / 2;

            if (check(mid)) {
                res = mid;
                r = mid - 1;
            } else {
                l = mid + 1;
            }
        }

        cout << res << "\n";
    }

    return 0;
}