Where could a third country inhabitant go to study pure mathematics/theoretical physics?

The quality of university level education in developing countries( North africa in my case) is mediocre at best,especially in the sciences(my interests lie primarly in mathematics).I've found that the appropriate places for getting this education would be France or Russia ,more specifally Ens and l'École Polytechnique in Paris( I'm aware that going to The classes préparatoires aux grandes écoles is strongly advised,but how can I avoid going there if possible?) and the National Research University Higher School of Economics in Moscow(which teaches in Russian which I will vigourously try to learn). Can study in my original country for a little while then go there? How do each of them cost? How can I proceed to achieve this almost impossible goal?