public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int N = sc . nextInt ( ) ;
  Integer [ ] L = new Integer [ 2 * N ] ;
  for ( int i = 0 ;
  i < 2 * N ;
  i ++ ) {
    L [ i ] = sc . nextInt ( ) ;
  }
  Arrays . sort ( L , Collections . reverseOrder ( ) ) ;
  int ans = 0 ;
  for ( int i = 0 ;
  i < N ;
  i ++ ) {
    ans += Math . min ( L [ 2 * i ] , L [ 2 * i + 1 ] ) ;
  }
  out . println ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int N = sc . nextInt ( ) ; Integer [ ] L = new Integer [ 2 * N ] ; for ( int i = 0 ; i < 2 * N ; i ++ ) { L [ i ] = sc . nextInt ( ) ; } Arrays . sort ( L , Collections . reverseOrder ( ) ) ; int ans = 0 ; for ( int i = 0 ; i < N ; i ++ ) { ans += Math . min ( L [ 2 * i ] , L [ 2 * i + 1 ] ) ; } out . println ( ans ) ; }
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