/in/foo.cc: In function 'int main()':
/in/foo.cc:56:9: error: 'pow' was not declared in this scope
   asum+=pow(2.0,i);
         ^~~
/in/foo.cc:56:9: note: suggested alternative: 'putw'
   asum+=pow(2.0,i);
         ^~~
         putw