bool M1;
#define look_memory cerr<<abs(&M2-&M1)/1024.0/1024<<" MB\n"
#define look_time cerr<<(clock()-Time)*1.0/CLOCKS_PER_SEC<<'\n'
#include <cstdio>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <cstring>
#include <array>
#include <algorithm>
#include <queue>
#include <vector>
#include <bitset>
#include <ctime>
#include <cstdlib>
#include <random>
#include <set>
#include <ctime>
#include <map>
#include <stack>
#include <unordered_map>
#include <assert.h>
#define i128 __int128
#define ll long long
#define uint unsigned
#define ull unsigned long long
#define fo(a,b,c) for(ll a=b;a<=c;++a)
#define re(a,b,c) for(ll a=b;a>=c;--a)
#define pii pair<ll,ll>
#define pdd pair<db,db>
#define fi first
#define pb push_back
#define se second
#define ite set<pii> ::iterator
#define vite vector<ll> ::iterator
using namespace std;
const ll mod=998244353;
inline ll gi()
{
	ll x = 0, f = 1;
	char ch = getchar();
	while(ch < '0' || ch > '9')
	{
		if (ch == '-')
			f = -1;
		ch = getchar();
	}
	while(ch >= '0' && ch <= '9')
	{
		x = (x<<1) + (x<<3) + (ch^48);
		ch = getchar();
	}
	return x * f;
}
ll _=1;
const ll inf=2e17+5,iinf=1e9;
const ll N=1000005;
ll t[N],c[N],n;
map<ll,ll> mp;
ll ck(ll v)
{
	ll z=0,rem=0;
	fo(i,2,n)
	{
		ll delt=t[i]-t[i-1];
		if(delt*v>=abs(c[i]-c[i-1]))
		{
			delt=t[i]-t[z];
			if((delt*v>=abs(c[i]-c[z])||z==0)&&rem==0) rem=i-1;
			continue;
		}
		ll ok=0;
		while(z!=i)
		{
			if(z==0)
			{
				ok=1;
				break;
			}
			else
			{
				delt=t[i]-t[z];
				if(delt*v>=abs(c[i]-c[z]))
				{
					ok=1;
					break;
				}
			}
			z++;
			z=max(z,rem);
		}
		if(ok)
		{
			z=i-1;
			rem=0;
		}
		else return 0;
	}
	return 1;
}
void sol()
{
	n=gi();
	fo(i,1,n)
	{
		t[i]=gi();
		c[i]=gi();
	}
	ll ans=-1;
	ll l=0,r=1000000000;
	while(l<=r)
	{
		ll mid=(l+r)/2;
		if(ck(mid))
		{
			ans=mid;
			r=mid-1;
		}
		else l=mid+1;
	}
	cout<<ans;
}
bool M2;
int main()
{
	int Time=clock();
	look_memory;
	_=gi();
	while(_--)
	{
		sol();
		printf("\n");
	}
	look_time;
	return 0;
}