/in/foo.cc: In function 'int main()':
/in/foo.cc:7:7: warning: statement has no effect [-Wunused-value]
  for(i;i<=a;i++)
       ^
/in/foo.cc:13:11: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<sum;
           ^