1 #include<stdio.h>
 2 #include <string.h>
 3 #include<math.h>
 4 #define Min(x,y) (x<y?x:y)
 5 const int INF=0x3f3f3f3f;
 6 const int MAXN=610;
 7 bool prim[1000010];
 8 int N,answer;
 9 int judge(int a,int b){
10         if(!prim[a]||!prim[b]||!prim[a+b]){
11             return Min(Min(a,b),fabs(a-b));
12         }
13         else return -1;
14 }
15 void pt(){
16     memset(prim,false,sizeof(prim));
17     prim[0]=prim[1]=true;
18     for(int i=2;i<=1000;i++){
19         if(!prim[i])for(int j=i*i;j<1000010;j+=i){
20             prim[j]=true;
21         }
22     }
23 }
24 int map[MAXN][MAXN],vis[MAXN],low[MAXN];
25 int v[MAXN];
26 void prime(){
27     int k;
28     int temp,flot=1;
29     answer=0;
30     memset(vis,0,sizeof(vis));
31     vis[0]=1;
32     for(int i=0;i<N;i++)low[i]=map[0][i];
33     for(int i=0;i<N;i++){
34             temp=INF;
35         for(int j=0;j<N;j++)
36             if(!vis[j]&&temp>low[j])
37                     temp=low[k=j];
38     if(temp==INF){
39         if(flot==N)printf("%d\n",answer);
40         else puts("-1");
41         break;
42     }
43         answer+=temp;
44         vis[k]=1;
45         flot++;
46         for(int j=0;j<N;j++)
47             if(!vis[j]&&low[j]>map[k][j])
48             low[j]=map[k][j];
49     }
50 }
51 int main(){
52         int T,t;
53         scanf("%d",&T);
54         while(T--){
55                     pt();
56                 memset(map,INF,sizeof(map));
57             scanf("%d",&N);
58             for(int i=0;i<N;i++)scanf("%d",&v[i]);
59             for(int i=0;i<N;i++)
60             for(int j=i+1;j<N;j++){
61                     t=judge(v[i],v[j]);
62                 if(t>=0){
63                     if(t<map[i][j])map[i][j]=map[j][i]=t;
64                 }
65             }
66             prime();
67         }
68     return 0;
69 }