foo.cc: In function 'int main()':
foo.cc:11:12: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(y%4==0&&y%100!=0||y%400==0)
      ~~~~~~^~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。