#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;

}