/in/foo.cc: In function 'int main()':
/in/foo.cc:12:13: warning: array subscript has type 'char' [-Wchar-subscripts]
  while(sum[i])
             ^
/in/foo.cc:14:14: warning: array subscript has type 'char' [-Wchar-subscripts]
   cout<<sum[i];
              ^