2020 AIME I Problem 1

In \triangle A B C with A B=A C, point D lies strictly between A and C on side \small\overline{A C}, and point E lies strictly between A and B on side \small\overline{A B} such that A E=E D=D B=B C. The degree measure of \angle A B C is \frac{m}{n}, where m and n are relatively prime positive integers. Find m+n.