D

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define _test   int _TEST; cin>>_TEST; while(_TEST--)

int main()
{
    _test
    {
        int n;
        cin>>n;

        vector<pair<ll int, ll int>> vp(n);
        for(auto &[l, r]: vp)       cin>>l>>r;

        ll int ans=1e9, low=0, high=1e9, mid;

        auto poss = [&](int k)
        {
            ll int x=0, y=0;

            for(auto [a, b]: vp)
            {
                x -= k;
                y += k;

                x = max(x, a);
                y = min(y, b);

                if(x > y)       return false;
            }

            return true;
        };

        while(low <= high)
        {
            int mid = (low + high)/2;

            if(poss(mid))   ans=mid, high=mid-1;
            else            low=mid+1;
        }

        cout<<ans<<"\n";
    }
}