olympiade mathematique marocaine 1993

[img]http://latex.codecogs.com/gif.latex?soit~~f~~une~~fonction~~definie~~sur~~\mathbb{N}^{*}~~et~~verifie~~la~~relation~~:\\\\\fbox{\forall%20~~m~,~n~\epsilon%20~\mathbb{N}^{*}~on~a~:~~f\left%20[%20f(m)+f(n)%20\right%20]=m+n~~calculer~:~f(1993).}[/img]