> #include <stdio.h>
> int main()
> {
> 	int cases,a,b;
> 	scanf("%d",&cases);
> 	while(cases--)
> 	{
> 		scanf("%d %d",&a,&b);
> 		if(b>a||(a%2==0&&b%2==1)||(a%2==1&&b%2==0))
> 		printf("impossible\n");
> 		else
> 		printf("%d %d\n",(a+b)/2,(a-b)/2);
> 	}
> 	return 1;
> }
能接受么 ？a,b都要大于等于0，