foo.cc: In function 'int main()':
foo.cc:38:7: error: 'rg' was not declared in this scope
  for (rg int k=1;k<=maxv;k++)
       ^~
foo.cc:38:18: error: 'k' was not declared in this scope
  for (rg int k=1;k<=maxv;k++)
                  ^
foo.cc:2:13: error: expected ';' before 'long'
 #define int long long
             ^
foo.cc:41:11: note: in expansion of macro 'int'
   for (rg int j=k;j<=maxv;j+=k)  now+=(pre[j+k-1]-pre[j-1])*(j/k);
           ^~~
foo.cc:41:19: error: 'j' was not declared in this scope
   for (rg int j=k;j<=maxv;j+=k)  now+=(pre[j+k-1]-pre[j-1])*(j/k);
                   ^

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