15. Fill in the circles with the natural numbers from 1 to 16 (each number must be used exactly once), so that the sum of the numbers in the 4 circles connected by the same straight line is equal. This is called an 8th-order magic star, and this equal number is called the magic sum of the 8th-order magic star. Therefore, the magic sum of the 8th-order magic star is $\qquad$, and continue to complete the following 8th-order magic star.

Fill in the circles with the natural numbers from 1 to 16 (each number must be used exactly once), so that the sum of the numbers in the 4 circles connected by the same straight line is equal. This is called an 8th-order magic star, and this equal number is called the magic sum of the 8th-order magic star. Therefore, the magic sum of the 8th-order magic star is $\qquad$, and continue to complete the following 8th-order magic star.
Analysis: Each number is on two lines, with a total of 8 lines, so there are 8 magic sums, and each number is repeated twice; therefore, according to the universal formula: Magic sum $\times 8=(1+2+3+\cdots+36) \times 2$; Magic sum $=(1+2+\cdots+16) \times 2 \div 8=34$; the completed figure is as shown above: