foo.cc: In function 'int main()':
foo.cc:8:6: warning: 'x' is used uninitialized in this function [-Wuninitialized]
  if(x%100==0)
     ~^~~~
foo.cc:22:6: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
   sum=sum+1;
   ~~~^~~~~~
foo.cc:26:4: warning: 'i' may be used uninitialized in this function [-Wmaybe-uninitialized]
    if(a==i)
    ^~

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