public static void main ( String args [ ] ) {
  Scanner scan = new Scanner ( System . in ) ;
  int t = scan . nextInt ( ) ;
  k : while ( t -- > 0 ) {
    int n = scan . nextInt ( ) ;
    int [ ] a = new int [ n ] ;
    for ( int i = 0 ;
    i < n ;
    i ++ ) {
      a [ i ] = scan . nextInt ( ) ;
    }
    int [ ] res = new int [ n ] ;
    int mx = 0 ;
    int [ ] b = new int [ n + 1 ] ;
    for ( int i = 0 ;
    i < n ;
    i ++ ) {
      if ( mx < a [ i ] ) {
        res [ i ] = a [ i ] ;
        ++ b [ a [ i ] ] ;
      }
      else if ( mx > a [ i ] ) {
        System . out . println ( "-1" ) ;
        continue k ;
      }
      mx = Math . max ( mx , a [ i ] ) ;
    }
    ArrayList < Integer > ar = new ArrayList < Integer > ( ) ;
    for ( int i = 1 ;
    i <= n ;
    i ++ ) {
      if ( b [ i ] == 0 ) {
        ar . add ( i ) ;
      }
    }
    int k = 0 ;
    for ( int i = 0 ;
    i < n ;
    i ++ ) {
      if ( res [ i ] == 0 ) {
        res [ i ] = ar . get ( k ) ;
        ++ k ;
      }
    }
    mx = 0 ;
    for ( int i = 0 ;
    i < n ;
    i ++ ) {
      mx = Math . max ( mx , res [ i ] ) ;
      if ( mx != a [ i ] ) {
        System . out . println ( "-1" ) ;
        continue k ;
      }
    }
    for ( int i = 0 ;
    i < n ;
    i ++ ) {
      System . out . print ( res [ i ] + " " ) ;
    }
    System . out . println ( ) ;
  }
}

public static void main ( String args [ ] ) { Scanner scan = new Scanner ( System . in ) ; int t = scan . nextInt ( ) ; k : while ( t -- > 0 ) { int n = scan . nextInt ( ) ; int [ ] a = new int [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { a [ i ] = scan . nextInt ( ) ; } int [ ] res = new int [ n ] ; int mx = 0 ; int [ ] b = new int [ n + 1 ] ; for ( int i = 0 ; i < n ; i ++ ) { if ( mx < a [ i ] ) { res [ i ] = a [ i ] ; ++ b [ a [ i ] ] ; } else if ( mx > a [ i ] ) { System . out . println ( " - 1" ) ; continue k ; } mx = Math . max ( mx , a [ i ] ) ; } ArrayList < Integer > ar = new ArrayList < Integer > ( ) ; for ( int i = 1 ; i <= n ; i ++ ) { if ( b [ i ] == 0 ) { ar . add ( i ) ; } } int k = 0 ; for ( int i = 0 ; i < n ; i ++ ) { if ( res [ i ] == 0 ) { res [ i ] = ar . get ( k ) ; ++ k ; } } mx = 0 ; for ( int i = 0 ; i < n ; i ++ ) { mx = Math . max ( mx , res [ i ] ) ; if ( mx != a [ i ] ) { System . out . println ( " - 1" ) ; continue k ; } } for ( int i = 0 ; i < n ; i ++ ) { System . out . print ( res [ i ] + " ▁ " ) ; } System . out . println ( ) ; } }
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