2014 AIME II Problem 12

Suppose that the angles of \triangle ABC satisfy \cos(3A)+\cos(3B)+\cos(3C)=1. Two sides of the triangle have lengths 10 and 13. There is a positive integer m so that the maximum possible length for the remaining side of \triangle ABC is \sqrt{m}. Find m.

Leading zeroes must be inputted, so if your answer is 34, then input 034

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.