CH-SMO 2021 Problem 8

Let $\triangle ABC$ be a triangle with $AB =AC$ and $\angle BAC = 20^{\circ}$ . Let $D$ be point on the side $AB$ such that $\angle BCD = 70^{\circ}$ . Let $E$ be point on the side $AC$ such that $\angle CBE = 60^{\circ}$ . Determine the value of angle $\angle CDE$ .