/in/foo.cc: In function 'int main()':
/in/foo.cc:13:17: warning: format '%ld' expects argument of type 'long int*', but argument 2 has type 'long long int*' [-Wformat=]
  scanf("%ld", &n);
                 ^
/in/foo.cc:20:19: warning: format '%ld' expects argument of type 'long int', but argument 2 has type 'int' [-Wformat=]
  printf("%ld", sum);
                   ^