     function repayUSDS( uint256 amountRepaid ) external nonReentrant{
       ...		
       usds.safeTransferFrom(msg.sender, address(usds), amountRepaid);

       // Have USDS remember that the USDS should be burned
       liquidizer.incrementBurnableUSDS( amountRepaid );
       ...
     }
function _possiblyBurnUSDS() internal{
        ...
	uint256 usdsBalance = usds.balanceOf(address(this));
	if ( usdsBalance >= usdsThatShouldBeBurned )
	{
		// Burn only up to usdsThatShouldBeBurned.
		// Leftover USDS will be kept in this contract in case it needs to be burned later.
		_burnUSDS( usdsThatShouldBeBurned );
    		usdsThatShouldBeBurned = 0;
	}
	else
	{
		// The entire usdsBalance will be burned - but there will still be an outstanding balance to burn later
		_burnUSDS( usdsBalance );
		usdsThatShouldBeBurned -= usdsBalance;

		// As there is a shortfall in the amount of USDS that can be burned, liquidate some Protocol Owned Liquidity and
		// send the underlying tokens here to be swapped to USDS
		dao.withdrawPOL(salt, usds, PERCENT_POL_TO_WITHDRAW);
		dao.withdrawPOL(dai, usds, PERCENT_POL_TO_WITHDRAW);
	}
}
