/in/foo.cc: In function 'int main()':
/in/foo.cc:11:47: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   11 |                         res+=months[2]+(y%4==0&&y%100||y%400==0);
      |                                         ~~~~~~^~~~~~~
/in/foo.cc:17:9: error: 'return0' was not declared in this scope
   17 |         return0;
      |         ^~~~~~~