How can I get only the real eigenvalues of a complex eigenvalue problem?

I have a large complex eigenvalue problem, and I am using eigs(A,B,k,sigma) to solve the problem. A and B are both large, sparse complex matrices. For instance, if k=400, sigma='sm', then I get about 100 real eigenvalues, 150 imaginary eigenvalues, and 150 complex eigenvalues. This is very computationally expensive, however, I am only interested in the real eigenvalues. Is there any way to calculate only the real eigenvalues please?