最短（略

http://acm.pku.edu.cn/JudgeOnline/problem?id=2301
いずれ（略

main(s,d,k){
  for(gets();~scanf(k="%d %d\n",&s,&d);
    printf(s<0|s%2?"impossible\n":k,s+d,s/=2))s-=d;
}