char*z;c;main(int w,int**v){for(w=asprintf(&z,"%512s%c%511s",v[1],0,v[2])/2;w--;z[w]=c%10+48)c=z[w]%16+z[w+512]%16+c/10;z+=strspn(z,"0");puts(*z?z:--z);exit(0);}