#include<bits/stdc++.h>
using namespace std;
constexpr int N=5005;
int n;
struct Point
{
    int x,y;
}p[N];
long double distance(const Point &a,const Point &b)
{
    return sqrtl((long long)(a.x-b.x)*(a.x-b.x)+(long long)(a.y-b.y)*(a.y-b.y));
}
long double dp[N];
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr),cout.tie(nullptr);
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>p[i].x>>p[i].y;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=i;j++)
            dp[i]=max(dp[i],dp[j-1]+distance(p[i],p[j]));
    long double ans=0;
    for(int i=1;i<=n;i++)
        ans=max(ans,dp[i]);
    cout<<fixed<<setprecision(15)<<ans;
    return 0;
}