public static void main ( String [ ] args ) {
  Scanner input = new Scanner ( System . in ) ;
  int n = input . nextInt ( ) ;
  int k = input . nextInt ( ) ;
  int a [ ] = new int [ n ] ;
  long sum = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    a [ i ] = input . nextInt ( ) ;
    sum += a [ i ] ;
  }
  for ( int i = 0 ;
  ;
  i ++ ) {
    long rd = Math . round ( ( i * k + sum * 1.0 ) / ( i + n * 1.0 ) ) ;
    if ( rd == k ) {
      System . out . println ( i ) ;
      return ;
    }
  }
}

public static void main ( String [ ] args ) { Scanner input = new Scanner ( System . in ) ; int n = input . nextInt ( ) ; int k = input . nextInt ( ) ; int a [ ] = new int [ n ] ; long sum = 0 ; for ( int i = 0 ; i < n ; i ++ ) { a [ i ] = input . nextInt ( ) ; sum += a [ i ] ; } for ( int i = 0 ; ; i ++ ) { long rd = Math . round ( ( i * k + sum * 1.0 ) / ( i + n * 1.0 ) ) ; if ( rd == k ) { System . out . println ( i ) ; return ; } } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (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)))) (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) dimensions: (dimensions) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (identifier))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_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 (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (expression_statement (assignment_expression left: (identifier) right: (array_access array: (identifier) index: (identifier)))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) update: (update_expression (identifier)) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (binary_expression left: (identifier) right: (decimal_floating_point_literal)))) right: (parenthesized_expression (binary_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_floating_point_literal))))))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier)))) (return_statement)))))))