#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
typedef vector<vector<ll>> Mat;
#define int long long
const int N=5e3+10,mod=1e9+7,inf=1e9+1,P=998244353;
const double pi=acos(-1.0),esp=1e-9;
const ll INF=1e18;
int x[N],y[N];
double dp[N];
double dis(int i,int j){
	return hypot(x[i]-x[j],y[i]-y[j]);
}
void solve()
{
	int n;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>x[i]>>y[i];
		for(int j=1;j<i;j++){
			dp[i]=max(dp[i],dp[j-1]+dis(i,j));
		}
		//cout<<dp[i]<<'\n';
	}
	cout<<fixed<<setprecision(12)<<dp[n]<<'\n';
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    int t=1;
    //cin>>t;
    while(t--)
        solve();
    return 0;
}