#include <bits/stdc++.h> using namespace std; #define int long long #define double long double struct nd { double x, y; }; nd dis[100005]; bool cmp(nd xx, nd yy) { if (xx.x != yy.x) return xx.x < yy.x; return xx.y < yy.y; } double mhd(int x1, int y1, int x2, int y2) { return 1.0*abs(x1-x2) + 1.0*abs(y1-y2); } double jld(int x1, int y1, int x2, int y2) { return 1.0*sqrt(1.0*(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)); } signed main() { freopen("pair.in", "r", stdin); freopen("pair.out", "w", stdout); int t; cin >> t; while (t--) { int n; cin >> n; for (int i = 1; i <= n; i++) { cin >> dis[i].x >> dis[i].y; } if (n<= 1000) { double maxn = 0; for (int i = 1; i < n; i++) { for (int j = i+1; j <= n; j++) { maxn = max(maxn,1.0*mhd(dis[i].x,dis[i].y,dis[j].x,dis[j].y)/ jld(dis[i].x,dis[i].y,dis[j].x,dis[j].y)); } } printf("%.12lf\n", maxn); } else { sort(dis+1, dis+n+1, cmp); double maxn = 0; for (int i = 1; i < n; i++) { maxn = max(maxn,1.0*mhd(dis[i].x,dis[i].y,dis[i+1].x,dis[i+1].y)/ jld(dis[i].x,dis[i].y,dis[i+1].x,dis[i+1].y)); } printf("%.12lf\n", maxn); } } return 0; }