/in/foo.cc: In function 'int main()':
/in/foo.cc:8:6: warning: unused variable 'i' [-Wunused-variable]
  int i,n,sum;
      ^
/in/foo.cc:14:9: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
    sum++; 
         ^