#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <set>
#include <queue>
#include <map>

using namespace std;

const long long inf = 2000000007;

struct point
{
	double x, y;
	point(double x, double y) : x(x), y(y) {}
};

point operator+(const point &a, const point &b)
{
	return point(a.x + b.x, a.y + b.y);
}

point operator-(const point &a, const point &b)
{
	return point(a.x - b.x, a.y - b.y);
}


double dist(point a, point b)
{
	return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
}

vector<point > p;
double dp[1000][1000];

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);

	//freopen("important.in", "r", stdin);freopen("important.out", "w", stdout);

	int n;
	cin >> n;

	double x, y;
	for (int i = 0; i < n; i++)
	{
		cin >> x >> y;
		p.push_back(point(x, y));
	}

	for (int i = 0; i < n; i++)
		for (int j = 0; j < n; j++)
			if (abs(i - j) > 2)
				dp[i][j] = inf;

	for (int i = 0; i < n - 3; i++)
	{
		dp[i][i + 3] = min(dist(p[i], p[i + 2]), dist(p[i + 1], p[i + 3]));
		for (int j = 4; i + j < n; j++)
		{
			for (int k = i + 1; k < i + j; k++)
				dp[i][i + j] = min(dp[i][i + j], dp[i][k] + dp[k][i + j] + dist(p[i], p[k]) + dist(p[k], p[i+j]));
		}
	}

	/*for (int i = 0; i < n; i++)
	{
		for (int j = 0; j < n; j++)
			cout << dp[i][j] << " ";
		cout << endl;
	}*/
	cout << fixed;
	cout << setprecision(10) << dp[0][n - 1] << endl;

	//system("PAUSE");

	return 0;
}