foo.cc: In function ‘int main()’:
foo.cc:14:30: error: unable to find numeric literal operator ‘operator""；’
   14 |                         lead=2；
      |                              ^~~
foo.cc:14:30: note: use ‘-fext-numeric-literals’ to enable more built-in suffixes
foo.cc:16:38: error: lvalue required as left operand of assignment
   16 |         if (month=4||month=6||month=9||month=11)
      |                                     ~^~~~~~~
foo.cc:19:74: error: lvalue required as left operand of assignment
   19 |         {       if (month=1||month=3||month=5||month=7||month=8||month=10||month=12)
      |                                                                        ~~^~~~~~~