#include<bits/stdc++.h> using namespace std; #define int long long mt19937 rng(114514191); int t,n; struct node{ int x,y; }a[100005]; long double ans; signed main(){ freopen("pair.in","r",stdin); freopen("pair.out","w",stdout); cin>>t; while(t--){ ans=-1; cin>>n; for(int i=1;i<=n;i++)cin>>a[i].x>>a[i].y; int p=1000000; while(p--){ int bb=rng()%n+1,b=rng()%n+1; ans=max(ans,(1.0*(abs(a[bb].x-a[b].x)+abs(a[bb].y-a[b].y)))/(sqrt(1.0*(a[bb].x-a[b].x)*(a[bb].x-a[b].x)+1.0*(a[bb].y-a[b].y)*(a[bb].y-a[b].y)))); } printf("%.10lf\n",ans); } return 0; }