/in/foo.cc: In function 'int main()':
/in/foo.cc:13:16: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(year%4==0 && year%100!=0 || year%400==0)
      ~~~~~~~~~~^~~~~~~~~~~~~~
/in/foo.cc:5:17: warning: variable 'days' set but not used [-Wunused-but-set-variable]
  int year,month,days;
                 ^~~~