  Consider quantum harmonic oscillator, perturbed by an even almost-periodic
complex-valued potential with bounded derivative and primitive. Suppose that we
know the first correction to the spectral asymptotics
$\{\Delta\mu_n\}_{n=0}^\infty$ ($\Delta\mu_n=\mu_n-\mu_n^0+o(n^{-1/4})$, where
$\mu_n^0$ and $\mu_n$ is the spectrum of the unperturbed and the perturbed
operators, respectively). We obtain the formula that recovers the frequencies
and the Fourier coefficients of the perturbation.
