// 'inplace' is okay
void RemoveGapsFromLabelImage(const ImgInt& labels, ImgInt* out)
{
int width = labels.Width();
int height = labels.Height();
out->Reset(width, height);
std::vector<int> used;
int x, y;
// scan image and create vector of all labels found
for (y=0 ; y<height ; y++)
{
for (x=0 ; x<width ; x++)
{
int a = labels(x,y);
if (iFind(used, a) < 0)
{
used.push_back(a);
}
}
}
// scan image, replacing labels
for (y=0 ; y<height ; y++)
{
for (x=0 ; x<width ; x++)
{
int a = labels(x,y);
int newlabel = iFind(used, a);
assert( newlabel >= 0 );
(*out)(x,y) = newlabel;
}
}
}
int main()
{
int i,j,n,e,tx,ty;
double ans;
while(scanf("%d",&n) != EOF)
{
for(i=0;i<n;i++)
scanf("%lf%lf",&x[i],&y[i]);
e=0;
for(i=0;i<n;i++)
for(j=i+1;j<n;j++)
{
u[e]=i;
v[e]=j;
w[e]=iDistance(i,j);
e++;
}
for(i=0;i<n;i++)
p[i]=i;
for(i=0;i<e;i++)
r[i]=i;
qsort(r,e,sizeof(r[0]),cmp);
ans=0.0;
for(i=0;i<e;i++)
{
tx=iFind(u[r[i]]);
ty=iFind(v[r[i]]);
if(tx!=ty)
{
p[tx]=ty;
ans+=w[r[i]];
}
}
printf("%.2f\n",ans);
}
return 0;
}
int iFind(int x)
{
return p[x]==x?x:(p[x]=iFind(p[x]));
}
