foo.cc: In function ‘int main()’:
foo.cc:10:51: error: expected ‘)’ before ‘!’ token
   10 |                         if ((year%4==0 && year%100!+0) || year%400==0)){
      |                             ~                     ^
      |                                                   )
foo.cc:12:26: error: expected ‘)’ before ‘else’
   12 |                         }
      |                          ^
      |                          )
   13 |                         else {
      |                         ~~~~
foo.cc:10:28: note: to match this ‘(’
   10 |                         if ((year%4==0 && year%100!+0) || year%400==0)){
      |                            ^
foo.cc:24:32: error: expected ‘;’ before ‘}’ token
   24 |                         days=31
      |                                ^
      |                                ;
   25 |     }
      |     ~