#include<bits/stdc++.h>
using namespace std;
#define double long double
const int N = 5005;
int n;
pair<int, int> a[N];
double f[N], ma[N];

double p2(double x) {
    return x * x;
}

double dis(pair<int, int> a, pair<int, int> b) {
    return sqrt(p2(a.first - b.first) + p2(a.second - b.second));
}

void solve() {
    cin >> n;
    for(int i = 1; i <= n; i ++ ) {
        cin >> a[i].first >> a[i].second;
    }

    for(int i = 2; i <= n; i ++ ) {
        for(int j = 1; j < i; j ++ ) {
            f[i] = max(f[i], ma[j - 1] + dis(a[i], a[j]));
            ma[i] = max(f[i], ma[i - 1]);
        }
    }

    cout << fixed << setprecision(9) << ma[n] << "\n";
}

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
#if 0
    freopen("D:\\CLionWorkPlace\\problemSeting\\in.txt", "r", stdin);
    freopen("D:\\CLionWorkPlace\\problemSeting\\out.txt", "w", stdout);
#endif
    int t = 1;
    // cin >> t;
    for(int i = 1; i <= t; i ++ ) {
        solve();
    }
}