EARNINGS PER SHARE - Basic earnings per share of common stock (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Basic and diluted earnings per share:
Net income	$ 230,733	$ 593,993
Weighted average common shares outstanding, basic	2,855,253	2,843,775
Weighted average common shares outstanding, diluted	2,855,253	2,843,775
Net income per share (basic)	$ 0.08	$ 0.21
Net income per share (diluted)	$ 0.08	$ 0.21
Options outstanding	0	0