In this problem: 1364E - X-OR ,the discription said "Exit immediately after receiving −1 and you will see wrong answer verdict. Otherwise, you can get an arbitrary verdict because your solution will continue to read from a closed stream." .

And in this submission 83742870, I followed this instruction by using if(val==-1)return 0;(in line 53,67,68,84), and I got a "wrong answer" . But after that ,I change the sentence from if(val==-1)return 0; to 'if(val1==-1){while(1);return 0;}' , and I got a "Accept" 83742993.

I have no idea what is going on.....