private static long solve ( int n , int [ ] counter ) {
  if ( ! isPossible ( n , counter ) ) {
    return 0 ;
  }
  long output = 1 ;
  for ( int i = 0 ;
  i < n / 2 ;
  i ++ ) {
    output *= 2 ;
    output %= 1000000007 ;
  }
  return output ;
}

private static long solve ( int n , int [ ] counter ) { if ( ! isPossible ( n , counter ) ) { return 0 ; } long output = 1 ; for ( int i = 0 ; i < n / 2 ; i ++ ) { output *= 2 ; output %= 1000000007 ; } return output ; }
(method_declaration (modifiers) type: (integral_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (integral_type) name: (identifier)) (formal_parameter type: (array_type element: (integral_type) dimensions: (dimensions)) name: (identifier))) body: (block (if_statement condition: (parenthesized_expression (unary_expression operand: (method_invocation name: (identifier) arguments: (argument_list (identifier) (identifier))))) consequence: (block (return_statement (decimal_integer_literal)))) (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: (binary_expression left: (identifier) right: (decimal_integer_literal))) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (identifier) right: (decimal_integer_literal))) (expression_statement (assignment_expression left: (identifier) right: (decimal_integer_literal))))) (return_statement (identifier))))