#include<bits/stdc++.h>
#define int long long
using namespace std;
inline int read()
{
	int sum=0,f=1;
	char ch=getchar();
	while(!isdigit(ch)){if(ch=='-')f*=-1;ch=getchar();}
	while(isdigit(ch)){sum=sum*10+ch-48;ch=getchar();}
	return sum*f;
}
int n;
int t[1000005];
int c[1000005];
bool ach(int x,int y,int v)
{
	return abs(t[x]-t[y])*v >= abs(c[x]-c[y]);
}
inline bool check(int v)
{
	t[n+1]=2e9;c[n+1]=0;
	int num=n;
	for(int i=n-1;i>=1;i--)
	{
		
//		cout<<ach(i+1,i,v)<<" ";
		
		if(ach(i+1,i,v)) continue;
		
		
//		cout<<num+1<<" "<<i<<" "<<v<<endl;
//		cout<<ach(num+1,i,v)<<endl;
		
		
		if(ach(num+1,i+1,v))
		{
			if(ach(num,i,v) || ach(num+1,i,v)) num=i;
			else return 0;
			continue;
		}
		
		if(ach(num+1,i,v)) num=i;
		else return 0;
	}
	return 1;
}
inline bool sub()
{
	int c1=-1,c2=-1;
	for(int i=1;i<=n;i++)
	{
		if(c1==c[i] || c2==c[i]) continue;
		if(c1==-1) c1=c[i];
		else if(c2==-1) c2=c[i];
		else return 0;
	}
	cout<<0<<endl;
	return 1;
}
inline void solve()
{
	n=read();
	for(int i=1;i<=n;i++) t[i]=read(),c[i]=read();
	if(sub()) return;
	int L=1,R=1000000000,ans=-1;
	while(L<=R)
	{
		int mid=(L+R)>>1;
		if(check(mid)) R=mid-1,ans=mid;
		else L=mid+1;
	}
	cout<<ans<<endl;
}
signed main()
{
	int T;
	T=read();
	while(T--) solve();
	return 0;
}