interface IERC20 {
  /**
   * @dev Returns the amount of tokens in existence.
   */
  function totalSupply() external view returns (uint256);

  /**
   * @dev Returns the amount of tokens owned by `account`.
   */
  function balanceOf(address account) external view returns (uint256);

  /**
   * @dev Moves `amount` tokens from the caller's account to `recipient`.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transfer(address recipient, uint256 amount) external returns (bool);

  /**
   * @dev Returns the remaining number of tokens that `spender` will be
   * allowed to spend on behalf of `owner` through {transferFrom}. This is
   * zero by default.
   *
   * This value changes when {approve} or {transferFrom} are called.
   */
  function allowance(address owner, address spender) external view returns (uint256);

  /**
   * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * IMPORTANT: Beware that changing an allowance with this method brings the risk
   * that someone may use both the old and the new allowance by unfortunate
   * transaction ordering. One possible solution to mitigate this race
   * condition is to first reduce the spender's allowance to 0 and set the
   * desired value afterwards:
   * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
   *
   * Emits an {Approval} event.
   */
  function approve(address spender, uint256 amount) external returns (bool);

  /**
   * @dev Moves `amount` tokens from `sender` to `recipient` using the
   * allowance mechanism. `amount` is then deducted from the caller's
   * allowance.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transferFrom(
    address sender,
    address recipient,
    uint256 amount
  ) external returns (bool);

  // underlying function is not available for Aave tokens
  function underlying (  ) external view returns ( address );

  function liquidateBorrow ( address borrower, uint256 repayAmount, address cTokenCollateral ) external returns ( uint256 );
  /************
   * The mint function transfers an asset into the CompFi protocol, which begins 
   * accumulating interest based on the current Supply Rate for the asset. 
   * The user receives a quantity of cTokens equal to the underlying 
   * tokens supplied, divided by the current Exchange Rate.
   * **********/
  function mint ( uint256 mintAmount ) external returns ( uint256 );
  /**********
   * redeem function converts a specified quantity of cTokens into the underlying asset, 
   * and returns them to the user.
   * redeemTokens - numberr of tokens to convert to the underlying token.
   * RETURN: 0 on success, otherwise an Error code.
   * ********/
  function redeem( uint redeemTokens ) external returns ( uint );
  
  /**
   * redeem underlying function converts cTokens into a specified quantity of the 
   * underlying asset, and returns them to the user.
   * redeemAmount - number of underlying tokens desired, depends on the exchange rate
   **/
    // available only for Compound tokens, like cUSDC or cETH
    function redeemUnderlying(uint redeemAmount) external returns (uint);

  /**
   * @dev Emitted when `value` tokens are moved from one account (`from`) to
   * another (`to`).
   *
   * Note that `value` may be zero.
   */
  event Transfer(address indexed from, address indexed to, uint256 value);

  /**
   * @dev Emitted when the allowance of a `spender` for an `owner` is set by
   * a call to {approve}. `value` is the new allowance.
   */
  event Approval(address indexed owner, address indexed spender, uint256 value);
}
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
function allowance(address owner, address spender) external view returns (uint256);

/**
 * @dev Returns the remaining number of tokens that `spender` will be
 * allowed to spend on behalf of `owner` through {transferFrom}. This is
 * zero by default.
 *
 * This value changes when {approve} or {transferFrom} are called.
 */