foo.cc: In function 'int main()':
foo.cc:5:5: error: 'scanf_s' was not declared in this scope; did you mean 'scanf'?
    5 |     scanf_s("%d %d", &year, &month);
      |     ^~~~~~~
      |     scanf
foo.cc:13:10: error: expected primary-expression before ':' token
   13 |     case :
      |          ^
foo.cc:14:10: error: expected primary-expression before ':' token
   14 |     case :
      |          ^
foo.cc:15:10: error: expected primary-expression before ':' token
   15 |     case :
      |          ^
foo.cc:16:10: error: expected primary-expression before ':' token
   16 |     case :printf("30\n"); break;
      |          ^
foo.cc:19:5: error: return-statement with no value, in function returning 'int' [-fpermissive]
   19 |     return ;
      |     ^~~~~~

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