foo.cc:21:21: error: stray '@' in program
   21 |   njnu19210448 LV 8 @ 1 个月前
      |                     ^
foo.cc:19:1: error: expected unqualified-id before numeric constant
   19 | 0
      | ^
foo.cc:45:5: error: redefinition of 'int main()'
   45 | int main()
      |     ^~~~
foo.cc:5:5: note: 'int main()' previously defined here
    5 | int main(){
      |     ^~~~

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