interface DividendPayingTokenInterface {
  /// @notice View the amount of dividend in wei that an address can withdraw.
    /// @param _owner The address of a token holder.
    /// @return The amount of dividend in wei that `_owner` can withdraw.
    function dividendOf(address _owner) external view returns(uint256);

    /// @notice Distributes ether to token holders as dividends.
    /// @dev SHOULD distribute the paid ether to token holders as dividends.
    ///  SHOULD NOT directly transfer ether to token holders in this function.
    ///  MUST emit a `DividendsDistributed` event when the amount of distributed ether is greater than 0.
    function distributeDividends() external payable;

    /// @notice Withdraws the ether distributed to the sender.
    /// @dev SHOULD transfer `dividendOf(msg.sender)` wei to `msg.sender`, and `dividendOf(msg.sender)` SHOULD be 0 after the transfer.
    ///  MUST emit a `DividendWithdrawn` event if the amount of ether transferred is greater than 0.
    function withdrawDividend() external;

    /// @dev This event MUST emit when ether is distributed to token holders.
    /// @param from The address which sends ether to this contract.
    /// @param weiAmount The amount of distributed ether in wei.
    event DividendsDistributed(
        address indexed from,
        uint256 weiAmount
    );

    /// @dev This event MUST emit when an address withdraws their dividend.
    /// @param to The address which withdraws ether from this contract.
    /// @param weiAmount The amount of withdrawn ether in wei.
    event DividendWithdrawn(
        address indexed to,
        uint256 weiAmount
    );
}
/// @title Dividend-Paying Token Interface
/// @author Roger Wu (https://github.com/roger-wu)
/// @dev An interface for a dividend-paying token contract.
function withdrawDividend() external;

/// @notice Withdraws the ether distributed to the sender.
/// @dev SHOULD transfer `dividendOf(msg.sender)` wei to `msg.sender`, and `dividendOf(msg.sender)` SHOULD be 0 after the transfer.
///  MUST emit a `DividendWithdrawn` event if the amount of ether transferred is greater than 0.