#include <bits/stdc++.h>using namespace std;#define F first#define S second#define mpr make_pair#define sqr(x) ((x)*(x))const int N = 205;const double eps = 1e-5;typedef pair< int,int > pr;typedef pair< pr,pr > prr;int n,c,cnt,cntb;pr a[N];vector< int > g[N];int d[N],b[N];int stk[N],instk[N],top;inline int in(int x=0) { scanf("%d",&x);return x; }void clr() {	cntb=cnt=top=0;	for(int i=0;i<N;i++) g[i].clear();	memset(d,0,sizeof(d)),memset(b,0,sizeof(b)),memset(instk,0,sizeof(instk));}double Dist(pr x,pr y) { return sqrt((double)sqr(x.F-y.F)+sqr(x.S-y.S)); }void Tarjan(int u,int fa) {	d[u]=++cnt,stk[++top]=u,instk[u]=1;int dfsn=cnt;	for(int i=0,v;i<(int)g[u].size();i++) if((v=g[u][i])!=fa) {		if(!d[v]) Tarjan(v,u);		if(instk[v]) d[u]=min(d[u],d[v]);	}	if(d[u]==dfsn) {		for(++cntb;stk[top]!=u;top--) {			b[stk[top]]=cntb,instk[stk[top]]=0;		}b[stk[top]]=cntb,instk[stk[top--]]=0;	}//	cout<<u<<":"<<d[u]<<" "<<dfsn<<endl;}int check(double x) {	clr();	for(int i=0;i<c;i++) for(int j=i&1 ? i+1 : i+2;j<c;j++)		if(Dist(a[i],a[j])<x*2) g[i].push_back(j^1),g[j].push_back(i^1);//	cout<<"("<<i<<","<<j<<")"<<Dist(a[i],a[j])<<endl,	for(int i=0;i<c;i++) if(!d[i]) Tarjan(i,i);	/*	cout<<x<<endl;	for(int i=0;i<c;i++) {		cout<<i<<":"<<endl;		for(int j=0;j<(int)g[i].size();j++) cout<<g[i][j]<<" ";		cout<<endl;	}	for(int i=0;i<c;i++) cout<<b[i]<<" ";cout<<endl;	cout<<"-------------------------"<<endl;*/		for(int i=0;i<c;i++) if(b[i]==b[i^1]) return 0;	return 1;}int main() {//	freopen("in.in","r",stdin);	while(~scanf("%d",&n)) {		c=0;		for(int i=1;i<=n;i++) {			int x=in(),y=in();			a[c++]=mpr(x,y);			x=in(),y=in();			a[c++]=mpr(x,y);		}		double l=0.0,r=20000.0,mid;		while(r-l > eps) {			mid=(l+r)/2.0;			if(check(mid)) l=mid;			else r=mid;		}printf("%.2lf\n",mid);	}return 0;}