contract ERC20 is Context, IERC20 {
	using SafeMath for uint256;

	mapping(address => uint256) private _balances;

	mapping(address => mapping(address => uint256)) private _allowances;

	uint256 private _totalSupply;

	/**
	 * @dev See {IERC20-totalSupply}.
	 */
	function totalSupply() public view returns (uint256) {
		return _totalSupply;
	}

	/**
	 * @dev See {IERC20-balanceOf}.
	 */
	function balanceOf(address account) public view returns (uint256) {
		return _balances[account];
	}

	/**
	 * @dev See {IERC20-transfer}.
	 *
	 * Requirements:
	 *
	 * - `recipient` cannot be the zero address.
	 * - the caller must have a balance of at least `amount`.
	 */
	function transfer(address recipient, uint256 amount) public returns (bool) {
		_transfer(_msgSender(), recipient, amount);
		return true;
	}

	/**
	 * @dev See {IERC20-allowance}.
	 */
	function allowance(address owner, address spender)
		public
		view
		returns (uint256)
	{
		return _allowances[owner][spender];
	}

	/**
	 * @dev See {IERC20-approve}.
	 *
	 * Requirements:
	 *
	 * - `spender` cannot be the zero address.
	 */
	function approve(address spender, uint256 amount) public returns (bool) {
		_approve(_msgSender(), spender, amount);
		return true;
	}

	/**
	 * @dev See {IERC20-transferFrom}.
	 *
	 * Emits an {Approval} event indicating the updated allowance. This is not
	 * required by the EIP. See the note at the beginning of {ERC20};
	 *
	 * Requirements:
	 * - `sender` and `recipient` cannot be the zero address.
	 * - `sender` must have a balance of at least `amount`.
	 * - the caller must have allowance for `sender`'s tokens of at least
	 * `amount`.
	 */
	function transferFrom(
		address sender,
		address recipient,
		uint256 amount
	) public returns (bool) {
		_transfer(sender, recipient, amount);
		_approve(
			sender,
			_msgSender(),
			_allowances[sender][_msgSender()].sub(
				amount,
				"ERC20: transfer amount exceeds allowance"
			)
		);
		return true;
	}

	/**
	 * @dev Atomically increases the allowance granted to `spender` by the caller.
	 *
	 * This is an alternative to {approve} that can be used as a mitigation for
	 * problems described in {IERC20-approve}.
	 *
	 * Emits an {Approval} event indicating the updated allowance.
	 *
	 * Requirements:
	 *
	 * - `spender` cannot be the zero address.
	 */
	function increaseAllowance(address spender, uint256 addedValue)
		public
		returns (bool)
	{
		_approve(
			_msgSender(),
			spender,
			_allowances[_msgSender()][spender].add(addedValue)
		);
		return true;
	}

	/**
	 * @dev Atomically decreases the allowance granted to `spender` by the caller.
	 *
	 * This is an alternative to {approve} that can be used as a mitigation for
	 * problems described in {IERC20-approve}.
	 *
	 * Emits an {Approval} event indicating the updated allowance.
	 *
	 * Requirements:
	 *
	 * - `spender` cannot be the zero address.
	 * - `spender` must have allowance for the caller of at least
	 * `subtractedValue`.
	 */
	function decreaseAllowance(address spender, uint256 subtractedValue)
		public
		returns (bool)
	{
		_approve(
			_msgSender(),
			spender,
			_allowances[_msgSender()][spender].sub(
				subtractedValue,
				"ERC20: decreased allowance below zero"
			)
		);
		return true;
	}

	/**
	 * @dev Moves tokens `amount` from `sender` to `recipient`.
	 *
	 * This is internal function is equivalent to {transfer}, and can be used to
	 * e.g. implement automatic token fees, slashing mechanisms, etc.
	 *
	 * Emits a {Transfer} event.
	 *
	 * Requirements:
	 *
	 * - `sender` cannot be the zero address.
	 * - `recipient` cannot be the zero address.
	 * - `sender` must have a balance of at least `amount`.
	 */
	function _transfer(
		address sender,
		address recipient,
		uint256 amount
	) internal {
		require(sender != address(0), "ERC20: transfer from the zero address");
		require(recipient != address(0), "ERC20: transfer to the zero address");

		_balances[sender] = _balances[sender].sub(
			amount,
			"ERC20: transfer amount exceeds balance"
		);
		_balances[recipient] = _balances[recipient].add(amount);
		emit Transfer(sender, recipient, amount);
	}

	/** @dev Creates `amount` tokens and assigns them to `account`, increasing
	 * the total supply.
	 *
	 * Emits a {Transfer} event with `from` set to the zero address.
	 *
	 * Requirements
	 *
	 * - `to` cannot be the zero address.
	 */
	function _mint(address account, uint256 amount) internal {
		require(account != address(0), "ERC20: mint to the zero address");

		_totalSupply = _totalSupply.add(amount);
		_balances[account] = _balances[account].add(amount);
		emit Transfer(address(0), account, amount);
	}

	/**
	 * @dev Destroys `amount` tokens from `account`, reducing the
	 * total supply.
	 *
	 * Emits a {Transfer} event with `to` set to the zero address.
	 *
	 * Requirements
	 *
	 * - `account` cannot be the zero address.
	 * - `account` must have at least `amount` tokens.
	 */
	function _burn(address account, uint256 amount) internal {
		require(account != address(0), "ERC20: burn from the zero address");

		_balances[account] = _balances[account].sub(
			amount,
			"ERC20: burn amount exceeds balance"
		);
		_totalSupply = _totalSupply.sub(amount);
		emit Transfer(account, address(0), amount);
	}

	/**
	 * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
	 *
	 * This is internal function is equivalent to `approve`, and can be used to
	 * e.g. set automatic allowances for certain subsystems, etc.
	 *
	 * Emits an {Approval} event.
	 *
	 * Requirements:
	 *
	 * - `owner` cannot be the zero address.
	 * - `spender` cannot be the zero address.
	 */
	function _approve(
		address owner,
		address spender,
		uint256 amount
	) internal {
		require(owner != address(0), "ERC20: approve from the zero address");
		require(spender != address(0), "ERC20: approve to the zero address");

		_allowances[owner][spender] = amount;
		emit Approval(owner, spender, amount);
	}

	/**
	 * @dev Destroys `amount` tokens from `account`.`amount` is then deducted
	 * from the caller's allowance.
	 *
	 * See {_burn} and {_approve}.
	 */
	function _burnFrom(address account, uint256 amount) internal {
		_burn(account, amount);
		_approve(
			account,
			_msgSender(),
			_allowances[account][_msgSender()].sub(
				amount,
				"ERC20: burn amount exceeds allowance"
			)
		);
	}
}
/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20Mintable}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
function allowance(address owner, address spender)
		public
		view
		returns (uint256)
	{
		return _allowances[owner][spender];
	}
/**
 	 * @dev See {IERC20-allowance}.
 	 */