#include <iostream>
#include <cstdio>
#include <cstring>
#include <stack>
#include <map>
#include <cmath>

using namespace std;

#define eps 1e-5
const int N = 210;
const int M = 400010;

int n , m ;

int st[N] , top ;
bool mark[N];
int eh[N] , et[M] , nxt[M] , tot ;
struct node { double x , y ; }e[N];


void init()
{
    tot = 0 ;
    memset( eh , -1 , sizeof eh );
    memset( mark , false , sizeof mark );
}

void addedge( int u , int v ){
    et[tot] = v , nxt[tot] = eh[u] , eh[u] = tot ++ ;
    et[tot] = u , nxt[tot] = eh[v] , eh[v] = tot ++ ;
}

bool dfs( int u )
{
    if( mark[u] ) return true;
    if( mark[u^1] ) return false;
    mark[u] = true ;
    st[top++] = u ;
    for( int i = eh[u] ; ~i ; i = nxt[i] ){
        int v = et[i];
        if( !dfs(v^1) ) return false;
    }
    return true;
}

bool solve()
{
    for(int i = 0 ; i < 2 * n ; i += 2 ){
        if( !mark[i] && !mark[i+1] ){
            top = 0 ;
            if( !dfs(i) ){
                while( top > 0 ) mark[ st[--top] ] = false;
                if( !dfs(i+1) ) return false ;
            }
        }
    }
    return true;
}

inline double dis( int i , int j )
{
    return sqrt( ( e[i].x - e[j].x ) * ( e[i].x - e[j].x ) + ( e[i].y - e[j].y ) * ( e[i].y - e[j].y ) ) ;
}

bool test( double DIS )
{
    init();
    for( int i = 0 ; i < 2 * n ; i += 2 ){
        for( int j = i + 2 ; j < 2 * n ; j += 2 ){
            if( dis( i , j ) < DIS )addedge( i , j );
            if( dis( i , j^1 ) < DIS )addedge( i , j^1 );
            if( dis( i^1 , j ) < DIS )addedge( i^1 , j ) ;
            if( dis( i^1 , j^1 ) < DIS )addedge( i^1 , j^1 );
        }
    }
    return solve();
}


int main()
{
    #ifdef LOCAL
        freopen("in.txt","r",stdin);
    #endif // LOCAL
    ios::sync_with_stdio(0);

    while( ~scanf("%d",&n) ){
        for( int i = 0 ; i < 2 * n ; ++i ){
            scanf("%lf%lf",&e[i].x,&e[i].y);
        }

        double l = 0.0 , r = sqrt( pow(20000.0,2.0) + pow(20000.0,2.0) );
        while( l + eps <= r ){
            double m = ( l + r ) / 2.0 ;
            
            if( test(m) )
                l = m  ;
            else
                r = m - eps ;
        }
        printf("%.2lf\n",l/2);
    }
}