EARNINGS PER SHARE - Basic earnings per share of common stock (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic and diluted earnings per share:
Net income	$ 888,440	$ 949,027	$ 1,962,090	$ 1,122,820
Weighted average common shares outstanding (in shares)	2,850,124	2,836,998	2,847,042	2,833,130
Basic and dilutive net income per share	$ 0.31	$ 0.33	$ 0.69	$ 0.40
Options outstanding	0	0	0	0