#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<vector>
#include<queue>
#include<cmath>
#include<set>
using std::set;
using std::pair;
using std::swap;
using std::multiset;
using std::priority_queue;
#define pb(e) push_back(e)
#define sz(c) (int)(c).size()
#define mp(a, b) make_pair(a, b)
#define all(c) (c).begin(), (c).end()
#define iter(c) __typeof((c).begin())
#define cls(arr, val) memset(arr, val, sizeof(arr))
#define cpresent(c, e) (find(all(c), (e)) != (c).end())
#define rep(i, n) for(int i = 0; i < (int)n; i++)
#define tr(c, i) for(iter(c) i = (c).begin(); i != (c).end(); ++i)
const int N = 110;
const int INF = 0x3f3f3f3f;
typedef unsigned long long ull;
struct P {float x, y;P(float i = 0.0, float j = 0.0) :x(i), y(j) {}inline float calc(const P &k) const {return sqrt((x - k.x) * (x - k.x) + (y - k.y) * (y - k.y));}
}A[N];
struct PDI {int v;float s;PDI(int i = 0, float j = 0.0) :v(i), s(j) {}inline bool operator<(const PDI &k) const {return s > k.s;}
};
struct Prim {bool vis[N];int tot, head[N];float mincost[N];struct edge { int to; float w; int next; }G[(N * N) << 1];inline void init(int n) {tot = 0;rep(i, n + 1) {head[i] = -1;vis[i] = false;mincost[i] = INF;}}inline void add_edge(int u, int v, float w) {G[tot] = (edge){ v, w, head[u] }; head[u] = tot++;}inline void built(int n) {rep(i, n) scanf("%f %f", &A[i].x, &A[i].y);for (int i = 0; i < n; i++) {for (int j = 0; j < n; j++) {if (i == j) continue;add_edge(i + 1, j + 1, A[i].calc(A[j]));}}}inline void prim(int s = 1) {float ans = 0.0;priority_queue<PDI> q;q.push(PDI(s));for (int i = head[s]; ~i; i = G[i].next) {edge &e = G[i];q.push(PDI(e.to, mincost[e.to] = e.w));}vis[s] = true;while (!q.empty()) {PDI t = q.top(); q.pop();int u = t.v;if (vis[u]) continue;vis[u] = true;ans += mincost[u];for (int i = head[u]; ~i; i = G[i].next) {edge &e = G[i];if (mincost[e.to] > e.w && !vis[e.to]) {q.push(PDI(e.to, mincost[e.to] = e.w));}}}printf("%.2f\n", ans);}inline void solve(int n) {init(n), built(n), prim();}
}go;
int main() {
#ifdef LOCALfreopen("in.txt", "r", stdin);freopen("out.txt", "w+", stdout);
#endifint n;while (~scanf("%d", &n)) {go.solve(n);}return 0;
}