public static void main ( String [ ] args ) throws IOException {
  Scanner sc = new Scanner ( System . in ) ;
  int candies_a = 0 ;
  int candies_b = 0 ;
  int n = sc . nextInt ( ) ;
  int [ ] a = new int [ n ] ;
  int [ ] b = new int [ n ] ;
  a [ 0 ] = sc . nextInt ( ) ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) {
    int tmp = sc . nextInt ( ) ;
    a [ i ] = a [ i - 1 ] + tmp ;
  }
  b [ 0 ] = sc . nextInt ( ) ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) {
    int tmp = sc . nextInt ( ) ;
    b [ i ] = b [ i - 1 ] + tmp ;
  }
  int candies = a [ 0 ] + b [ n - 1 ] ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) {
    int tmp = a [ i ] + ( b [ n - 1 ] - b [ i - 1 ] ) ;
    if ( tmp > candies ) {
      candies = tmp ;
    }
  }
  System . out . print ( candies ) ;
}

public static void main ( String [ ] args ) throws IOException { Scanner sc = new Scanner ( System . in ) ; int candies_a = 0 ; int candies_b = 0 ; int n = sc . nextInt ( ) ; int [ ] a = new int [ n ] ; int [ ] b = new int [ n ] ; a [ 0 ] = sc . nextInt ( ) ; for ( int i = 1 ; i < n ; i ++ ) { int tmp = sc . nextInt ( ) ; a [ i ] = a [ i - 1 ] + tmp ; } b [ 0 ] = sc . nextInt ( ) ; for ( int i = 1 ; i < n ; i ++ ) { int tmp = sc . nextInt ( ) ; b [ i ] = b [ i - 1 ] + tmp ; } int candies = a [ 0 ] + b [ n - 1 ] ; for ( int i = 1 ; i < n ; i ++ ) { int tmp = a [ i ] + ( b [ n - 1 ] - b [ i - 1 ] ) ; if ( tmp > candies ) { candies = tmp ; } } System . out . print ( candies ) ; }
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