public static void main ( String [ ] args ) throws IOException {
  Scanner scanner = new Scanner ( System . in ) ;
  int n = scanner . nextInt ( ) ;
  while ( n -- > 0 ) {
    int s = scanner . nextInt ( ) ;
    Pair [ ] pairs = new Pair [ s ] ;
    for ( int i = 0 ;
    i < s ;
    i ++ ) {
      pairs [ i ] = new Pair ( scanner . nextInt ( ) , scanner . nextInt ( ) ) ;
    }
    Arrays . sort ( pairs ) ;
    int x = 0 , y = 0 ;
    boolean can = true ;
    String res = "" ;
    for ( int i = 0 ;
    i < s ;
    i ++ ) {
      if ( x <= pairs [ i ] . first && y <= pairs [ i ] . second ) {
        for ( int j = 0 ;
        j < pairs [ i ] . first - x ;
        j ++ ) {
          res += "R" ;
        }
        for ( int j = 0 ;
        j < pairs [ i ] . second - y ;
        j ++ ) {
          res += "U" ;
        }
        x = pairs [ i ] . first ;
        y = pairs [ i ] . second ;
      }
      else {
        can = false ;
        break ;
      }
    }
    if ( can ) {
      println ( "YES\n" + res ) ;
    }
    else {
      println ( "NO" ) ;
    }
  }
}

public static void main ( String [ ] args ) throws IOException { Scanner scanner = new Scanner ( System . in ) ; int n = scanner . nextInt ( ) ; while ( n -- > 0 ) { int s = scanner . nextInt ( ) ; Pair [ ] pairs = new Pair [ s ] ; for ( int i = 0 ; i < s ; i ++ ) { pairs [ i ] = new Pair ( scanner . nextInt ( ) , scanner . nextInt ( ) ) ; } Arrays . sort ( pairs ) ; int x = 0 , y = 0 ; boolean can = true ; String res = " " ; for ( int i = 0 ; i < s ; i ++ ) { if ( x <= pairs [ i ] . first && y <= pairs [ i ] . second ) { for ( int j = 0 ; j < pairs [ i ] . first - x ; j ++ ) { res += " R " ; } for ( int j = 0 ; j < pairs [ i ] . second - y ; j ++ ) { res += " U " ; } x = pairs [ i ] . first ; y = pairs [ i ] . second ; } else { can = false ; break ; } } if ( can ) { println ( " YES \n " + res ) ; } else { println ( " NO " ) ; } } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) (throws (type_identifier)) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (while_statement condition: (parenthesized_expression (binary_expression left: (update_expression (identifier)) right: (decimal_integer_literal))) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (array_type element: (type_identifier) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (type_identifier) dimensions: (dimensions_expr (identifier))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (object_creation_expression type: (type_identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal)) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (local_variable_declaration type: (boolean_type) declarator: (variable_declarator name: (identifier) value: (true))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (string_literal))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (field_access object: (array_access array: (identifier) index: (identifier)) field: (identifier))) right: (binary_expression left: (identifier) right: (field_access object: (array_access array: (identifier) index: (identifier)) field: (identifier))))) consequence: (block (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (binary_expression left: (field_access object: (array_access array: (identifier) index: (identifier)) field: (identifier)) right: (identifier))) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (identifier) right: (string_literal))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (binary_expression left: (field_access object: (array_access array: (identifier) index: (identifier)) field: (identifier)) right: (identifier))) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (identifier) right: (string_literal))))) (expression_statement (assignment_expression left: (identifier) right: (field_access object: (array_access array: (identifier) index: (identifier)) field: (identifier)))) (expression_statement (assignment_expression left: (identifier) right: (field_access object: (array_access array: (identifier) index: (identifier)) field: (identifier))))) alternative: (block (expression_statement (assignment_expression left: (identifier) right: (false))) (break_statement))))) (if_statement condition: (parenthesized_expression (identifier)) consequence: (block (expression_statement (method_invocation name: (identifier) arguments: (argument_list (binary_expression left: (string_literal) right: (identifier)))))) alternative: (block (expression_statement (method_invocation name: (identifier) arguments: (argument_list (string_literal))))))))))