7. If the expression $\frac{1}{1 \times 2}-\frac{1}{3 \times 4}+\frac{1}{5 \times 6}-\frac{1}{7 \times 8}+\cdots-\frac{1}{2007 \times 2008}+\frac{1}{2009 \times 2010}$ is converted to a decimal, then the first digit after the decimal point is $\qquad$ .
Answer: 4