13. Fill in the small squares with 1 and 11 respectively, with one number in each small square, requiring that the sum of the 3 numbers in each of the 5 $3 \times 1$ rectangles be equal. The minimum value of this sum is

Fill in the small squares with 1 and 11 respectively, with one number in each small square, requiring that the sum of the 3 numbers in each of the 5 $3 \times 1$ rectangles be equal. The minimum value of this sum is
$16$