/in/foo.cc: In function 'int main()':
/in/foo.cc:9:7: warning: statement has no effect [-Wunused-value]
  for(a==1;a<=b;a++)
      ~^~~
/in/foo.cc:15:11: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<sum;
           ^