REDEEMABLE EQUITY - Summary of preferred stock (Details)	3 Months Ended	9 Months Ended
	Feb. 28, 2022 USD ($) $ / shares	Feb. 28, 2022 USD ($) $ / shares
Temporary Equity [Line Items]
Accrued Dividends	$ 1,242,000	$ 1,242,000
Series C Convertible Redeemable Preferred Stock
Temporary Equity [Line Items]
Liquidation preference (in dollars per share) | $ / shares	$ 25	$ 25
Original Proceeds, Net	$ 15,135,023	$ 15,135,023
Accrued Dividends	402,150	402,150
Redemption Amount	15,537,173	15,537,173
Liquidation Amount	$ 16,500,000	$ 16,500,000
Series D Convertible Redeemable Preferred Stock
Temporary Equity [Line Items]
Liquidation preference (in dollars per share) | $ / shares	$ 25	$ 25
Original Proceeds, Net	$ 31,574,000	$ 31,574,000
Accrued Dividends	840,300	840,300
Redemption Amount	32,414,600	32,414,600
Liquidation Amount	$ 34,500,000	$ 34,500,000