Income taxes (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Total taxable income (loss)	$ 832,510	$ (9,397)
UNITED STATES
Total taxable income (loss)	(20,260)	$ (9,397)
HONG KONG
Total taxable income (loss)	(34,119)
CHINA
Total taxable income (loss)	$ 886,888