#include<bits/stdc++.h>
using namespace std;
int n,a[105],maxx,minn=100000,t,m;
int main()
{
	cin>>t;
	for(int l=1;l<=t;l++)
	{
		cin>>m>>n;
		for(int i=1;i<=n;i++)
			cin>>a[i],maxx=max(maxx,a[i]),minn=min(minn,a[i]);
		sort(a+1,a+n+1);
		int k=0,g=0;
		for(int i=maxx;i<=maxx+minn;i++)
		{
			int h=1,t=n;
			k=0;
			for(;h<=t;)
			{
				if(a[t]==i) t--;
				else if(a[h]+a[t]==i) t--,h++;
				else {k=1;break;}
			//	cout<<h<<' '<<t<<endl;
			}
			if(k==0) {cout<<"possible\n";g=1;break;}
		}
		if(g<1) cout<<"impossible\n";
	}
	return 0;
}

题目

样例
4
1 1
47 
3 5
10 8 10 1 1 
3 5
3 9 10 7 1 
6 11
1 1 1 2 1 1 1 1 1 1 1