26. For a cube with edge length of m cm, some of its faces are painted red, and then it is cut into small cubes with edge length of 1 cm. The ratio of the number of small cubes with at least one red face to the number of small cubes with no red surface is 13:12. What is the minimum value of m at this time?
A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.
Official solution
answer: 5
Source: NuminaMath-1.5,
licensed Apache-2.0.
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