#include <iostream>
#include <cstring>
#include <cmath>
using namespace std;
struct point {double x,y;};
int n;
double maxp=0.0,per=0.0;
double rast (double x1, double x2, double y1, double y2)
{
    double d;
    d=sqrt(pow(x1-x2,2)+pow(y1-y2,2));
    return d;
}
int main ()
{
    cin >> n;
    point p[n];
    for (int i=0; i<n; i++)
        cin >> p[i].x >> p[i].y;
    for (int i=0; i<n; i++)
        for (int j=0; j<n; j++)
            for (int k=0; k<n; k++)
            {
                per=0.0;
                per=per+rast(p[i].x,p[j].x,p[i].y,p[j].y);
                per=per+rast(p[j].x,p[k].x,p[j].y,p[k].y);
                per=per+rast(p[k].x,p[i].x,p[k].y,p[i].y);
                if (per>maxp) maxp=per;
            }
    cout << maxp;
    return 0;
}