public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int q = sc . nextInt ( ) ;
  while ( q -- > 0 ) {
    int n = sc . nextInt ( ) ;
    int a [ ] = new int [ n ] ;
    for ( int i = 0 ;
    i < n ;
    i ++ ) a [ i ] = sc . nextInt ( ) ;
    Arrays . sort ( a ) ;
    int g = 1 ;
    for ( int i = n - 1 ;
    i > 0 ;
    i -- ) {
      if ( a [ i ] - a [ i - 1 ] == 1 ) g = 2 ;
    }
    System . out . println ( g ) ;
  }
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int q = sc . nextInt ( ) ; while ( q -- > 0 ) { int n = sc . nextInt ( ) ; int a [ ] = new int [ n ] ; for ( int i = 0 ; i < n ; i ++ ) a [ i ] = sc . nextInt ( ) ; Arrays . sort ( a ) ; int g = 1 ; for ( int i = n - 1 ; i > 0 ; i -- ) { if ( a [ i ] - a [ i - 1 ] == 1 ) g = 2 ; } System . out . println ( g ) ; } }
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