#include <cstdio>#include <cstring>#include <algorithm>#include <cmath>using namespace std;const int INF = 0x3f3f3f3f;const int N = 1e3;struct Point {double x, y;}point[N];double dp[N][N];bool cmp(Point a, Point b) {if(a.x != b.x)return a.x < b.x;return a.y < b.y;}inline double dis(int i, int j) {double x = point[i].x - point[j].x;double y = point[i].y - point[j].y;return sqrt(x*x + y*y);}double tsp(int n) {for(int i = 1; i <= n; i++) {for(int j = 1; j < i; j++) {dp[i][j] = dp[j][i] = INF;}}for(int i = 1; i <= n; i++) {dp[i][1] = dis(i, 1);}for(int i = 2; i < n; i++) {for(int j = 1; j < i; j++) {dp[i+1][j] = dp[i][j] + dis(i, i+1);dp[i+1][i] = min(dp[i+1][i], dp[i][j] + dis(j, i+1));}}return dp[n][n-1] + dis(n, n-1);}int main() {int n;while(scanf("%d", &n) != EOF) {for(int i = 1; i <= n; i++) {scanf("%lf%lf", &point[i].x, &point[i].y);}sort(point+1, point+1+n, cmp);double ans = tsp(n);printf("%.2fn", ans);}return 0;}
