my country is the most populous country in the world. It now has about 1.3 billion people. The second place is India. Its population is 404 million less than that of China and 599 million more than that of the United States. What is the total population of the United States?
我国是世界人口最多的国家，现在大约有13亿人，排在第二的是印度，它的人口总数比中国少4.04亿，比美国多5.99亿，美国的人口总数是多少亿人？
<gadget id="calculator">13 - 4.04 - 5.99</gadget>
<output>2.97</output>

<result>2.97</result>