EARNINGS PER SHARE - Basic earnings per share of common stock (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Basic and diluted:
Net income	$ 319,275	$ 477,685	$ 454,300	$ 733,154
Weighted average common shares outstanding (in shares)	2,819,994	2,806,599	2,818,266	2,804,565
Basic and dilutive net income per share	$ 0.11	$ 0.17	$ 0.16	$ 0.26
Options outstanding	0	0	0	0