foo.cc: In function 'int main()':
foo.cc:6:22: warning: format '%d' expects argument of type 'int*', but argument 2 has type 'long long int*' [-Wformat=]
  scanf("%d%d", &n, &m);
                ~~    ^
foo.cc:6:22: warning: format '%d' expects argument of type 'int*', but argument 3 has type 'long long int*' [-Wformat=]
foo.cc:10:20: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long long int' [-Wformat=]
  printf("%d\n", sum);
                    ^
foo.cc:6:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。