foo.cc:21:19: error: stray ‘@’ in program
   21 |  12109俞天奇 LV 8 @ 3 年前
      |                   ^
foo.cc:19:1: error: expected unqualified-id before numeric constant
   19 | 1
      | ^
foo.cc:25:5: error: redefinition of ‘int main()’
   25 | int main()
      |     ^~~~
foo.cc:3:5: note: ‘int main()’ previously defined here
    3 | int main()
      |     ^~~~