public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int [ ] arr = new int [ n + 1 ] ;
  for ( int i = 1 ;
  i <= n ;
  i ++ ) arr [ i ] = sc . nextInt ( ) ;
  boolean thereIsAnswer = false ;
  outer : for ( int i = 1 ;
  i < 4 ;
  i ++ ) {
    for ( int j = i ;
    j < 4 ;
    j ++ ) {
      if ( j == i ) continue ;
      line src = new line ( i , arr [ i ] , j , arr [ j ] ) ;
      for ( int k = 1 ;
      k <= n ;
      k ++ ) {
        line other = src . getParallel ( k , arr [ k ] ) ;
        for ( int l = 1 ;
        l <= n && ! other . identical ( src ) ;
        l ++ ) {
          if ( ( src . passThroughPoint ( l , arr [ l ] ) || other . passThroughPoint ( l , arr [ l ] ) ) ) {
            thereIsAnswer = true ;
          }
          else {
            thereIsAnswer = false ;
            break ;
          }
        }
        if ( thereIsAnswer && ! other . identical ( src ) ) break outer ;
      }
    }
  }
  System . out . println ( thereIsAnswer ? "YES" : "NO" ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int [ ] arr = new int [ n + 1 ] ; for ( int i = 1 ; i <= n ; i ++ ) arr [ i ] = sc . nextInt ( ) ; boolean thereIsAnswer = false ; outer : for ( int i = 1 ; i < 4 ; i ++ ) { for ( int j = i ; j < 4 ; j ++ ) { if ( j == i ) continue ; line src = new line ( i , arr [ i ] , j , arr [ j ] ) ; for ( int k = 1 ; k <= n ; k ++ ) { line other = src . getParallel ( k , arr [ k ] ) ; for ( int l = 1 ; l <= n && ! other . identical ( src ) ; l ++ ) { if ( ( src . passThroughPoint ( l , arr [ l ] ) || other . passThroughPoint ( l , arr [ l ] ) ) ) { thereIsAnswer = true ; } else { thereIsAnswer = false ; break ; } } if ( thereIsAnswer && ! other . identical ( src ) ) break outer ; } } } System . out . println ( thereIsAnswer ? " YES " : " NO " ) ; }
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