14. Fill in the blanks with 1 and 10, using each number only once. It is required that the number in $\square$ equals the difference (larger minus smaller) of the two numbers above it to the left and right, and the number in $\mathrm{O}$ equals the sum of the two numbers above it to the left and right. Find: the value of $A$.

Fill in the blanks with 1 and 10, using each number only once. It is required that the number in $\square$ equals the difference (larger minus smaller) of the two numbers above it to the left and right, and the number in $\mathrm{O}$ equals the sum of the two numbers above it to the left and right. Find: the value of $A$.
【Answer】9

【Solution】As shown in the figure below