1 #include <bits/stdc++.h> 2 using namespace std; 3 #define pb push_back 4 #define _for(i,a,b) for(int i = (a);i < (b);i ++) 5 #define INF 100000003 6 #define ll long long 7 inline ll read() 8 { 9 ll ans = 0; 10 char ch = getchar(), last = ' '; 11 while(!isdigit(ch)) last = ch, ch = getchar(); 12 while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar(); 13 if(last == '-') ans = -ans; 14 return ans; 15 } 16 inline void write(ll x) 17 { 18 if(x < 0) x = -x, putchar('-'); 19 if(x >= 10) write(x / 10); 20 putchar(x % 10 + '0'); 21 } 22 23 double mincost[5003]; 24 bool used[5003]; 25 26 int V; 27 struct P 28 { 29 int x; 30 int y; 31 }; 32 P a[5003]; 33 double cal(P a,P b) 34 { 35 return sqrt((double)(a.x-b.x)*(a.x-b.x)+(double)(a.y-b.y)*(a.y-b.y)); 36 } 37 double MST() 38 { 39 _for(i,1,V+1) 40 { 41 mincost[i] = INF; 42 used[i] = false; 43 } 44 45 mincost[1] = 0; 46 double res = 0; 47 48 while(1) 49 { 50 int v = -1; 51 _for(u,1,V+1) 52 if(!used[u] && (v==-1 || mincost[u] < mincost[v])) 53 v = u; 54 55 if(v==-1) break; 56 used[v] = true; 57 res += mincost[v]; 58 59 _for(u,1,V+1) 60 mincost[u] = min(mincost[u],cal(a[v],a[u])); 61 } 62 return res; 63 } 64 65 int main() 66 { 67 V = read(); 68 _for(i,1,V+1) 69 a[i].x = read(),a[i].y = read(); 70 71 printf("%.2lf ",MST()); 72 return 0; 73 }