#include<bits/stdc++.h> using namespace std; struct node { double x,y; }a[1000001]; bool cmp1(node p,node q) { p.x+p.y<q.x+q.y; } bool cmp2(node p,node q) { p.y-p.x>q.y-q.x; } int main() { int t; cin>>t; while(t--) { int n; cin>>n; for(int i=1;i<=n;i++) { cin>>a[i].x>>a[i].y; } sort(a+1,a+1+n,cmp1); double ans=0; for(int i=1;i<n;i++) { double d1=abs(a[i].x-a[i+1].x)+abs(a[i].y-a[i+1].y); double d2=sqrt((a[i].x-a[i+1].x)*(a[i].x-a[i+1].x)+(a[i].y-a[i+1].y)*(a[i].y-a[i+1].y)); ans=max(ans,d1/d2); } sort(a+1,a+1+n,cmp2); for(int i=1;i<n;i++) { double d1=abs(a[i].x-a[i+1].x)+abs(a[i].y-a[i+1].y); double d2=sqrt((a[i].x-a[i+1].x)*(a[i].x-a[i+1].x)+(a[i].y-a[i+1].y)*(a[i].y-a[i+1].y)); ans=max(ans,d1/d2); } printf("%.12lf",ans); } return 0; }