#pragma GCC optimize(3)
#include <bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define N 5005
#define MOD 998244353
#define eps 1e-10
using namespace std;

struct Point {
    int x,y;
    Point(int x=0,int y=0):x(x),y(y){}
    Point operator-(const Point &B){return Point(x-B.x, y-B.y);}
    ll operator*(const Point &B){return (ll)x*B.x+(ll)y*B.y;}
};
double len(Point A){return sqrt(A*A);}
double dist(Point A,Point B){return len(A-B);}
int n;
Point p[N];
double g[N][N];
double f[N];
void solve()
{
    cin>>n;
    for(int i=1;i<=n;++i)
    {
        cin>>p[i].x>>p[i].y;
    }
    for(int j=1;j<=n;++j)
        for(int i=j-1;i>=1;--i)
            g[i][j] = max(g[i+1][j], dist(p[i],p[j]));

    for(int i=1;i<=n;++i)
    {
        f[i] = f[i-1];
        for(int j=0;j<=i-1;++j)
            f[i] = max(f[i], f[j]+g[j+1][i]);
        // cout<<f[i]<<' ';
    }
    cout<<f[n]<<'\n';
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout<<fixed<<setprecision(12);
    int T=1;
    // cin>>T;
    while(T--)
    {
        solve();
    }
    return 0;
}