UVA 12800

#include<bits/stdc++.h>
using namespace std;

#define sc( x ) scanf( "%d" , &x )
#define REP( i , n ) for( int i = 0 ; i < n ; ++i )
#define clr( t , val ) memset( t , val , sizeof( t ) )

#define pb push_back
#define all( v ) v.begin() , v.end()
#define SZ( v ) ((int)(v).size())

#define N 200
#define INF (1e10)

typedef vector< int > vi;
typedef long double ld;

struct Point{
    ld x ,y;
    Point(){ x = y = 0;}
    Point( ld x , ld y ) : x( x ) , y( y ) {}
    ld dist(){ return hypot( x , y );}
};

Point operator - ( const Point &A , const Point &B ){ return Point( A.x - B.x , A.y - B.y );}
Point operator + ( const Point &A , const Point &B ){ return Point( A.x + B.x , A.y + B.y );}
ld dist( const Point &A , const Point &B ){ return (B - A).dist();}
Point P[ N + 5 ];
bool used[ N + 5 ][ N + 5 ];
ld memo[ N + 5 ][ N + 5 ];
int n;
ld Dist( int a , int b ){
    if( (a + 1)%n == b ) return 0;
    return dist( P[ a ] , P[ b ] );
}
ld dp( int lo , int hi ){
    if( (lo + 3)%n == hi ) return 0;
    if( (lo + 2)%n == hi ) return 0;
    if( (lo + 1)%n == hi ) return 0;
    if( (lo + 0)%n == hi ) return 0;
    if( used[ lo ][ hi ] ) return memo[ lo ][ hi ];
    used[ lo ][ hi ] = 1;
    ld &dev = memo[ lo ][ hi ] = INF;
    for( int i = (lo + 1)%n ; i != hi ; i = (i + 2)%n )
        for( int j = (i + 1)%n ; j != (hi + 1)%n ; j = (j + 2)%n ){
            dev = min( dev , Dist( lo , i ) + Dist( i , j ) + Dist( j , hi ) + dp( lo , i ) + dp( i , j ) + dp( j , hi ) );
        }
    return dev;
}
int main(){
    while( sc( n ) == 1 ){
        n *= 2;
        REP( i , n ){
            double x , y;
            scanf( "%lf%lf" , &x , &y );
            P[ i ] = Point( x , y );
        }
        clr( used , 0 );
        printf( "%.4f\n" , (double) dp( 0 , n - 1 ) );
    }
}