foo.cc: In function 'int main()':
foo.cc:10:22: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(a%4==0||a%400==0&&a%100==0){
              ~~~~~~~~^~~~~~~~~~

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