Consider the 5 $\times$ 5 matrix

$$\begin{bmatrix} 1&2&3&4&5\\ 5&1 &2& 3 &4\\ 4&5&1&2&3\\ 3&4&5&1&2\\ 2&3&4&5&1 \end{bmatrix}$$

It is given that A has only one real eigenvalue. Then the real eigenvalue of A is