public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int N = Integer . parseInt ( sc . next ( ) ) ;
  HashMap < Integer , Pair > map = new HashMap < > ( ) ;
  ArrayList < Pair > l = new ArrayList < > ( ) ;
  for ( int i = 0 ;
  i < N ;
  i ++ ) {
    int c = Integer . parseInt ( sc . next ( ) ) ;
    for ( int j = 0 ;
    j < 3 ;
    j ++ ) {
      if ( j == 1 ) c -- ;
      else if ( j == 2 ) c += 2 ;
      if ( ! map . containsKey ( c ) ) {
        Pair p = new Pair ( c , 1 ) ;
        map . put ( c , p ) ;
        l . add ( p ) ;
      }
      else {
        Pair p = map . get ( c ) ;
        p . cnt ++ ;
      }
    }
  }
  Collections . sort ( l ) ;
  Pair res = l . get ( l . size ( ) - 1 ) ;
  System . out . println ( res . cnt ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int N = Integer . parseInt ( sc . next ( ) ) ; HashMap < Integer , Pair > map = new HashMap < > ( ) ; ArrayList < Pair > l = new ArrayList < > ( ) ; for ( int i = 0 ; i < N ; i ++ ) { int c = Integer . parseInt ( sc . next ( ) ) ; for ( int j = 0 ; j < 3 ; j ++ ) { if ( j == 1 ) c -- ; else if ( j == 2 ) c += 2 ; if ( ! map . containsKey ( c ) ) { Pair p = new Pair ( c , 1 ) ; map . put ( c , p ) ; l . add ( p ) ; } else { Pair p = map . get ( c ) ; p . cnt ++ ; } } } Collections . sort ( l ) ; Pair res = l . get ( l . size ( ) - 1 ) ; System . out . println ( res . cnt ) ; }
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