public static void main ( String [ ] args ) throws Exception {
  Scanner sc = new Scanner ( System . in ) ;
  int N = sc . nextInt ( ) ;
  int K = sc . nextInt ( ) ;
  int X = sc . nextInt ( ) ;
  int Y = sc . nextInt ( ) ;
  int price = ( N <= K ) ? N * X : ( K * X ) + ( ( N - K ) * Y ) ;
  System . out . println ( price ) ;
}

public static void main ( String [ ] args ) throws Exception { Scanner sc = new Scanner ( System . in ) ; int N = sc . nextInt ( ) ; int K = sc . nextInt ( ) ; int X = sc . nextInt ( ) ; int Y = sc . nextInt ( ) ; int price = ( N <= K ) ? N * X : ( K * X ) + ( ( N - K ) * Y ) ; System . out . println ( price ) ; }
(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)))) (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: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (ternary_expression condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (binary_expression left: (identifier) right: (identifier)) alternative: (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) right: (parenthesized_expression (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) right: (identifier))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))