#include <iostream>

#include <cstdio>

#include <sstream>

#include <cstring>

#include <map>

#include <cctype>

#include <set>

#include <vector>

#include <stack>

#include <queue>

#include <algorithm>

#include <cmath>

#include <bitset>

#define eps 1e-8

#define rap(i, a, n) for(int i=a; i<=n; i++)

#define rep(i, a, n) for(int i=a; i<n; i++)

#define lap(i, a, n) for(int i=n; i>=a; i--)

#define lep(i, a, n) for(int i=n; i>a; i--)

#define rd(a) scanf("%d", &a)

#define rlld(a) scanf("%lld", &a)

#define rc(a) scanf("%c", &a)

#define rs(a) scanf("%s", a)

#define pd(a) printf("%d\n", a);

#define plld(a) printf("%lld\n", a);

#define pc(a) printf("%c\n", a);

#define ps(a) printf("%s\n", a);

#define MOD 2018

#define LL long long

#define ULL unsigned long long

#define Pair pair<int, int>

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

#define _  ios_base::sync_with_stdio(0),cin.tie(0)

//freopen("1.txt", "r", stdin);

using namespace std;

const int maxn = 1e5 + , INF = 0x7fffffff, LL_INF = 0x7fffffffffffffff;

int n;

vector<int> G[maxn];

int vis[maxn], low[maxn], scc_clock, scc_cnt, sccno[maxn];

stack<int> S;

struct node

{

    int x, y;

}Node[maxn];

void dfs(int u)

{

    vis[u] = low[u] = ++scc_clock;

    S.push(u);

    for(int i = ; i < G[u].size(); i++)

    {

        int v = G[u][i];

        if(!vis[v])

        {

            dfs(v);

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

        }

        else if(!sccno[v])

        {

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

        }

    }

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

    {

        scc_cnt++;

        for(;;)

        {

            int x = S.top(); S.pop();

            sccno[x] = scc_cnt;

            if(x == u) break;

        }

    }

}

double dis(node a, node b)

{

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

}

void build(double mid)

{

    for(int i = ; i < maxn; i++) G[i].clear();

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

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

            if(i /  != j /  && dis(Node[i], Node[j]) < mid)

            {

                G[i].push_back(j ^ ); G[j].push_back(i ^ );

            }

}

void init()

{

    mem(vis, );

    mem(low, );

    mem(sccno, );

    scc_cnt = scc_clock = ;

}

bool check()

{

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

    {

        if(sccno[i] == sccno[i ^ ])

            return false;

    }

    return true;

}

int main()

{

    while(cin >> n)

    {

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

        {

            cin >> Node[i << ].x >> Node[i << ].y >> Node[(i << )  + ].x >> Node[(i << ) + ].y;

        }

        double l = , r = INF;

        while(r - l > eps)

        {

            init();

            double mid = l + (r - l) /(double) ;

            build(mid * );

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

                if(!vis[i]) dfs(i);

            if(check()) l = mid;

            else r = mid;

        }

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

    }

    return ;

}