import java.io.*;
import java.util.*;
class gambling 
{
  public static void main( String[] args ) throws IOException
  {
    BufferedReader bf = new BufferedReader( new InputStreamReader( System.in ) );
    while( true )
    {
      String line = bf.readLine();

      if ( line.equals( "0" ) )
      {
        break;
      }
      StringTokenizer st = new StringTokenizer( line, " " );
      int number_int = st.countTokens();
      
      if ( number_int <= 1 ) continue;
      int k = ( int ) ( ( double ) (number_int - 1) ) / 2;
      
      int a = ( int ) Math.floor( (double ) number_int / k );

      int b = number_int - ( k * a );

      int c = k - b;

      if ( number_int > 1 ){
      long vysl = 0;
      for ( int i = 0; i < number_int; i++ )
      {

	String s = st.nextToken();
        int tmp = Integer.parseInt( s );
	vysl += tmp;
	if ( i < c ) vysl += tmp;
      }
        System.out.print(  vysl + "\n" );
      }
    }
  }

}