#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];
inline bool check(int v)
{
	int pos=0,tim=2e9;
	for(int i=n-1;i>=1;i--)
	{
		
//		cout<<v<<" "<<pos<<" "<<tim<<endl;
//		cout<<abs(t[i]-t[i+1])*v<<" "<<abs(c[i]-c[i+1])<<endl;
//		cout<<abs(c[i]-pos)<<" "<<abs(tim-t[i])*v<<endl;
		
		if(abs(t[i]-t[i+1])*v >= abs(c[i]-c[i+1])) continue;
		if(abs(c[i]-pos) > abs(tim-t[i])*v) return 0;
		pos=c[i+1],tim=t[i+1];
	}
	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;
}