static void dfs ( int v , int par ) {
  d [ v ] [ 0 ] = 1 ;
  for ( Integer i : gr [ v ] ) {
    if ( i != par ) {
      dfs ( i , v ) ;
      for ( int j = 1 ;
      j <= k ;
      j ++ ) ans += d [ i ] [ j - 1 ] * d [ v ] [ k - j ] ;
      for ( int j = 1 ;
      j <= k ;
      j ++ ) d [ v ] [ j ] += d [ i ] [ j - 1 ] ;
    }
  }
}

static void dfs ( int v , int par ) { d [ v ] [ 0 ] = 1 ; for ( Integer i : gr [ v ] ) { if ( i != par ) { dfs ( i , v ) ; for ( int j = 1 ; j <= k ; j ++ ) ans += d [ i ] [ j - 1 ] * d [ v ] [ k - j ] ; for ( int j = 1 ; j <= k ; j ++ ) d [ v ] [ j ] += d [ i ] [ j - 1 ] ; } } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (integral_type) name: (identifier)) (formal_parameter type: (integral_type) name: (identifier))) body: (block (expression_statement (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (decimal_integer_literal)) right: (decimal_integer_literal))) (enhanced_for_statement type: (type_identifier) name: (identifier) value: (array_access array: (identifier) index: (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (block (expression_statement (method_invocation name: (identifier) arguments: (argument_list (identifier) (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: (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (identifier) right: (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: (expression_statement (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (identifier) right: (decimal_integer_literal))))))))))))