#include <bits/stdc++.h>
using LL = long long;

const int maxN = 5e3 + 5;
int n;
int x[maxN], y[maxN];
double f[maxN];
LL dis[maxN][maxN], max_dist[maxN][maxN];
int main() {
	std::ios::sync_with_stdio(false); std::cin.tie(nullptr);
	std::cin >> n;

	for(int i = 1; i <= n; i++) {
		std::cin >> x[i] >> y[i];
	}

	for(int i = 1; i <= n; i++) {
		for(int j = i; j <= n; j++) {
			dis[i][j] = 1ll * (x[i] - x[j]) * (x[i] - x[j]) + 1ll * (y[i] - y[j]) * (y[i] - y[j]);
		}
	}

	for(int j = 1; j <= n; j++) {
		for(int i = j; i >= 1; i--) {
			dis[i][j] = std::max(dis[i][j], dis[i + 1][j]);
		}
	}

	for(int i = 1; i <= n; i++) {
		for(int j = i; j <= n; j++) {
			max_dist[i][j] = std::max(max_dist[i][j - 1], dis[i][j]);
		}
	}

	f[0] = 0;
	for(int i = 1; i <= n; i++) {
		for(int j = i; j >= 1; j--) f[i] = std::max(f[i], f[j - 1] + sqrt(max_dist[j][i]));
	}

	std::cout << std::fixed << std::setprecision(15) << f[n] << "\n";
	return 0;
}