foo.cc: In function ‘int main()’:
foo.cc:23:16: warning: format ‘%lld’ expects argument of type ‘long long int’, but argument 2 has type ‘long int’ [-Wformat=]
   23 |     printf("%lld\n", sum);
      |             ~~~^     ~~~
      |                |     |
      |                |     long int
      |                long long int
      |             %ld