public static void main ( String [ ] args ) {
  Scanner scanner = new Scanner ( System . in ) ;
  int n = scanner . nextInt ( ) , ch = 0 , bic = 0 , back = 0 ;
  int a [ ] = new int [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    a [ i ] = scanner . nextInt ( ) ;
  }
  for ( int i = 0 ;
  i < n ;
  i += 3 ) {
    ch += a [ i ] ;
  }
  for ( int i = 1 ;
  i < n ;
  i += 3 ) {
    bic += a [ i ] ;
  }
  for ( int i = 2 ;
  i < n ;
  i += 3 ) {
    back += a [ i ] ;
  }
  int max = Math . max ( Math . max ( ch , bic ) , back ) ;
  if ( max == ch ) {
    System . out . println ( "chest" ) ;
  }
  else if ( max == bic ) {
    System . out . println ( "biceps" ) ;
  }
  else {
    System . out . println ( "back" ) ;
  }
}

public static void main ( String [ ] args ) { Scanner scanner = new Scanner ( System . in ) ; int n = scanner . nextInt ( ) , ch = 0 , bic = 0 , back = 0 ; int a [ ] = new int [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { a [ i ] = scanner . nextInt ( ) ; } for ( int i = 0 ; i < n ; i += 3 ) { ch += a [ i ] ; } for ( int i = 1 ; i < n ; i += 3 ) { bic += a [ i ] ; } for ( int i = 2 ; i < n ; i += 3 ) { back += a [ i ] ; } int max = Math . max ( Math . max ( ch , bic ) , back ) ; if ( max == ch ) { System . out . println ( " chest " ) ; } else if ( max == bic ) { System . out . println ( " biceps " ) ; } else { System . out . println ( " back " ) ; } }
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