g++ 3.1.1 issue

[Dmitry Kostenko]

I've downloaded & installed gcc 3.1.1 from
gcc.gnu.org, it compiled OK but I've got a problem:
gcc does compile c++ sources but is not
autoconfigured to find STL include headers.
for example, such main.C will compile:
int main()
{  return 0; }

and such file won't:

#include <iostream>
int main()
{
  std::cout << "Hello, World!\n";
  return 0;
}

when I say gcc main.C, it says <iostream>
not found, and std is not a namespace...

I've search to installation guide, it
doesn't say much about such problem.
Where to find documentation on gcc configuration.