  Let \phi((x_1,...,x_n),(y_1,...,y_n))=(x_1-y_1)^2+...+(x_n-y_n)^2. We say
that f:R^n -> C^n preserves distance d>=0 if for each x,y \in R^n \phi(x,y)=d^2
implies \phi(f(x),f(y))=d^2. We prove that if x,y \in R^n (n>=3) and
|x-y|=(\sqrt{2+2/n})^k \cdot (2/n)^l (k,l are non-negative integers) then there
exists a finite set {x,y} \subseteq S(x,y) \subseteq R^n such that each
unit-distance preserving mapping from S(x,y) to C^n preserves the distance
between x and y. It implies that each continuous map from R^n to C^n (n>=3)
preserving unit distance preserves all distances.
