public static void main ( String args [ ] ) {
  Scanner s = new Scanner ( System . in ) ;
  int t = s . nextInt ( ) ;
  while ( t -- != 0 ) {
    long n = s . nextLong ( ) ;
    long k = s . nextLong ( ) ;
    long times = n / k ;
    long ans = times * k ;
    long rem = n - ans ;
    ans += Math . min ( k / 2 , rem ) ;
    System . out . println ( ans ) ;
  }
}

public static void main ( String args [ ] ) { Scanner s = new Scanner ( System . in ) ; int t = s . nextInt ( ) ; while ( t -- != 0 ) { long n = s . nextLong ( ) ; long k = s . nextLong ( ) ; long times = n / k ; long ans = times * k ; long rem = n - ans ; ans += Math . min ( k / 2 , rem ) ; System . out . println ( ans ) ; } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (type_identifier) name: (identifier) dimensions: (dimensions))) 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: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (identifier) right: (identifier)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (identifier) right: (identifier)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (identifier) right: (identifier)))) (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (decimal_integer_literal)) (identifier))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))))