/in/foo.cc: In function 'int main()':
/in/foo.cc:8:27: error: unable to find numeric literal operator 'operator""n'
  for(long double i=1;i<=2*2n-1;i+=2)
                           ^~
/in/foo.cc:8:27: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes