#include <cstdio>

#include <cstring>

#include <string>

#include <cmath>

#include <iostream>

#include <algorithm>

#include <queue>

#include <cstdlib>

#include <stack>

#include <vector>

#include <set>

#include <map>

#define LL long long

#define mod 100000000

#define inf 0x3f3f3f3f

#define eps 1e-6

#define N 210

#define FILL(a,b) (memset(a,b,sizeof(a)))

#define lson l,m,rt<<1

#define rson m+1,r,rt<<1|1

#define PII pair<int,int>

using namespace std;

struct edge

{

    int v,next;

    edge() {}

    edge(int v,int next):v(v),next(next) {}

} e[N*N];

int n,m,scc,step,top,tot;

int head[N],dfn[N],low[N],belong[N],Stack[N];

bool instack[N];

void init()

{

    tot=;step=;

    scc=;top=;

    FILL(head,-);

    FILL(dfn,);

    FILL(low,);

    FILL(instack,false);

}

void addedge(int u,int v)

{

    e[tot]=edge(v,head[u]);

    head[u]=tot++;

}

void tarjan(int u)

{

    int v;

    dfn[u]=low[u]=++step;

    Stack[top++]=u;

    instack[u]=true;

    for(int i=head[u]; ~i; i=e[i].next)

    {

        v=e[i].v;

        if(!dfn[v])

        {

            tarjan(v);

            low[u]=min(low[u],low[v]);

        }

        else if(instack[v])

        {

            low[u]=min(low[u],dfn[v]);

        }

    }

    if(dfn[u]==low[u])

    {

        scc++;

        do

        {

            v=Stack[--top];

            instack[v]=false;

            belong[v]=scc;

        }

        while(v!=u);

    }

}

int judge()

{

    for(int i=; i<*n; i++)

        if(!dfn[i])tarjan(i);

    for(int i=; i<n; i++)

    {

        if(belong[i<<]==belong[i<<^])

        {

            return ;

        }

    }

    return ;

}

int lx[],ly[],rx[],ry[];

double dist(int a,int b,int x,int y)

{

    return sqrt((double)(a-x)*(a-x)+(double)(b-y)*(b-y));

}

void build(double m)

{

    for(int i=;i<n;i++)

        for(int j=i+;j<n;j++)

        {

            if(dist(lx[i],ly[i],lx[j],ly[j])+eps<*m)addedge(i<<,j<<|),addedge(j<<,i<<|);

            if(dist(lx[i],ly[i],rx[j],ry[j])+eps<*m)addedge(i<<,j<<),addedge(j<<|,i<<|);

            if(dist(rx[i],ry[i],lx[j],ly[j])+eps<*m)addedge(i<<|,j<<|),addedge(j<<,i<<);

            if(dist(rx[i],ry[i],rx[j],ry[j])+eps<*m)addedge(i<<|,j<<),addedge(j<<|,i<<);

        }

}

void solve()

{

    double l=,r=,ans=;

    while(r-l>eps)

    {

        double m=(l+r)/;

        init();

        build(m);

        if(judge())

        {

            ans=m;l=m;

        }

        else r=m;

    }

    printf("%.2f\n",ans);

}

int main()

{

    int a,b,c,u,v;

    char op[];

    while(scanf("%d",&n)>)

    {

        for(int i=;i<n;i++)

        {

            scanf("%d%d%d%d",&lx[i],&ly[i],&rx[i],&ry[i]);

        }

        solve();

    }

}