#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define LC(x) (x<<1)
#define RC(x) ((x<<1)+1)
#define MID(x,y) ((x+y)>>1)
#define CLR(arr,val) memset(arr,val,sizeof(arr))
#define FAST_IO ios::sync_with_stdio(false);cin.tie(0);
typedef pair<int, int> pii;
typedef long long LL;
const double PI = acos(-1.0);
const double eps = 1e-5;
const int N = 110;
const int M = N * N * 4;
struct edge
{
    int to, nxt;
    edge() {}
    edge(int _to, int _nxt): to(_to), nxt(_nxt) {}
};
pii P[N];
edge E[M];
int head[N << 1], tot;
int dfn[N << 1], low[N << 1], st[N << 1], belong[N << 1], ts, scc, top;
bitset < N << 1 > ins;
int n;

void init()
{
    CLR(head, -1);
    tot = 0;
    CLR(dfn, 0);
    CLR(low, 0);
    CLR(belong, 0);
    ts = scc = top = 0;
    ins.reset();
}
inline void add(int s, int t)
{
    E[tot] = edge(t, head[s]);
    head[s] = tot++;
}
void Tarjan(int u)
{
    dfn[u] = low[u] = ++ts;
    st[top++] = u;
    ins[u] = 1;
    int i, v;
    for (i = head[u]; ~i; i = E[i].nxt)
    {
        v = E[i].to;
        if (!dfn[v])
        {
            Tarjan(v);
            low[u] = min(low[u], low[v]);
        }
        else if (ins[v])

            low[u] = min(low[u], dfn[v]);
    }
    if (dfn[u] == low[u])
    {
        ++scc;
        do
        {
            v = st[--top];
            ins[v] = 0;
            belong[v] = scc;
        }
        while (u != v);
    }
}
inline double cal(const pii &a, const pii &b)
{
    return sqrt((a.first - b.first) * (a.first - b.first) + (a.second - b.second) * (a.second - b.second));
}
bool check(double r, int sz)
{
    init();
    int i, j;
    for (i = 0; i < sz; i += 2)
    {
        for (j = i + 2; j < sz; ++j)
        {
            double dx = cal(P[i], P[j]);
            if (dx < 2 * r)
            {
                add(i, j ^ 1);
                add(j, i ^ 1);
            }
        }
    }
    for (i = 1; i < sz; i += 2)
    {
        for (j = i + 1; j < sz; ++j)
        {
            double dx = cal(P[i], P[j]);
            if (dx < 2 * r)
            {
                add(i, j ^ 1);
                add(j, i ^ 1);
            }
        }
    }
    for (i = 0; i < sz; ++i)
        if (!dfn[i])
            Tarjan(i);
    for (i = 0; i < sz; ++i)
        if (belong[i] == belong[i ^ 1])
            return false;
    return true;
}
int main(void)
{
    int i;
    while (~scanf("%d", &n))
    {
        for (i = 0; i < (n << 1); i += 2)
            scanf("%d%d%d%d", &P[i].first, &P[i].second, &P[i | 1].first, &P[i | 1].second);
        double L = 0, R = 10000 * 1.45;
        double ans = 0;
        while (R - L >= eps)
        {
            double mid = (L + R) / 2.0;
            if (check(mid, n << 1))
            {
                L = mid;
                ans = mid;
            }
            else
                R = mid;
        }
        printf("%.2f\n", ans);
    }
    return 0;
}