1 #include<stdio.h>
2 #include<math.h>
3 #include<string.h>
4 #define M 999999999
5 #define N 2000000
6 int a[610],map[610][610];
7 int b[610],c[610],g[N];
8 int Min(int x,int y)
9 {
10 if(x>y)
11 return y;
12 else
13 return x;
14 }
15 void prim()
16 {
17 int i,j;
18 int flag=1;
19 memset(g,0,sizeof(g));
20 g[0]=1;g[1]=1;
21 for(i=2;i<=N;i++)
22 {
23 if(!g[i])
24 {
25 for(j=i+i;j<=N;j+=i)
26 g[j]=1;
27 }
28 }
29 }
30 int fun(int x,int y)
31 {
32 if(!g[x]||!g[y]||!g[x+y])
33 return 1;
34 else
35 return 0;
36 }
37 int main()
38 {
39 int tt,n,i,j,x,y;
40 scanf("%d",&tt);
41
42 prim();
43 while(tt--)
44 {
45 scanf("%d",&n);
46 for(i=1;i<=n;i++)
47 scanf("%d",&a[i]);
48 memset(map,0,sizeof(map));
49 memset(b,0,sizeof(b));
50
51 for(i=1;i<=n;i++)
52 {
53 for(j=i+1;j<=n;j++)
54 {
55 map[i][j]=map[j][i]=M;
56 if(fun(a[i],a[j]))
57 {
58 x=Min(a[i],a[j]);
59 if(a[i]>a[j])
60 y=a[i]-a[j];
61 else
62 y=a[j]-a[i];
63
64 map[i][j]=map[j][i]=Min(x,y);
65 }
66 }
67 }
68 c[1]=0;
69 for(i=2;i<=n;i++)
70 c[i]=map[1][i];
71 int t,flag=0;
72 t=1;
73 c[t]=0;
74 int sum=0;
75 while(b[t]==0)
76 {
77 b[t]=1;
78 for(i=1;i<=n;i++)
79 if(b[i]==0&&c[i]>map[t][i])
80 c[i]=map[t][i];
81 int min=M;
82 for(i=1;i<=n;i++)
83 if(b[i]==0&&min>c[i])
84 {
85 min=c[i];
86 t=i;
87 }
88 if(min!=M)
89 {
90 sum+=min;
91 }
92
93 }
94 for(i=1;i<=n;i++)
95 {
96 if(c[i]>=M)
97 {
98 flag=1;
99 break;
100 }
101 }
102 if(flag==0)
103 printf("%d\n",sum);
104 else
105 printf("-1\n");
106 }
107 return 0;
108 }
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