var
  i,n,z,m,k,j:longint;
  cost:double;
  x,y,a,p,b,rank:array[1..25000000]of longint;
  w:array[1..25000000]of double;
procedure sort(l,r:longint);
var i,j,k:longint;
  e,t:longint;
begin
  i:=l;
  j:=r;
  e:=w[l+random(r-l+1)];
  while i<=j do
  begin
    while e>w[i] do inc(i);
    while e<w[j] do dec(j);
    if i<=j then
    begin
    t:=w[i];w[i]:=w[j];w[j]:=t;
    k:=a[i];a[i]:=a[j];a[j]:=k;
    k:=b[i];b[i]:=b[j];b[j]:=k;
    inc(i);
    dec(j);
    end;
  end;
  if i<r then sort(i,r);
  if j>l then sort(l,j);
end;
function find(x:longint):longint;
begin
  if x<>p[x] then p[x]:=find(p[x]);
  find:=p[x];
end;
procedure union(x,y:longint);
begin
  x:=find(x);
  y:=find(y);
  if rank[x]>rank[y] then p[y]:=x else p[x]:=y;
  if rank[x]=rank[y] then inc(rank[y]);
end;
begin
assign(input,'unionday.in');reset(input);
assign(output,'unionday.out');rewrite(output);
  read(n);
  for i:=1 to n do
  read(x[i],y[i]);

  m:=0;
  for i:=1 to n do
    for j:=i+1 to n do
    begin
    inc(m);
    a[m]:=i;
    b[m]:=j;
    w[m]:=sqrt(sqr(x[i]-x[j])+sqr(y[i]-y[j]));
    end;

  sort(1,m);
  for i:=1 to n do
  begin
  p[i]:=i;
  rank[i]:=0;
  end;

  z:=0;
  cost:=0;
  for i:=1 to m do
  begin
    if find(a[i])<>find(b[i]) then
    begin
    union(a[i],b[i]);
    cost:=cost+w[i];
    end;
  end;

  writeln(cost:0:5);
end.