  We consider the classical self-dual Yang-Mills equation in 3+1-dimensional
Minkowski space. We have found an exact solution, which describes scattering of
$n$ plane waves. In order to write the solution in a compact form, it is
convenient to introduce a scattering operator $\hat{T}$. It acts in the direct
product of three linear spaces: 1) universal enveloping of $su(N)$ Lie algebra,
2) $n$-dimensional vector space and 3) space of functions defined on the unit
interval.
