Prime Ring Problem
Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 17642 Accepted Submission(s): 7945
Note: the number of first circle should always be 1.

You are to write a program that completes above process.
Print a blank line after each case.
6 8
Case 1: 1 4 3 2 5 6 1 6 5 2 3 4 Case 2: 1 2 3 8 5 6 7 4 1 2 5 8 3 4 7 6 1 4 7 6 5 8 3 2 1 6 7 4 3 8 5 2
#include<iostream>
using namespace std;
int n,vi[23];
int a[23],j;
bool isprime(int b,int c){
int m=b+c;
for(int i=2;i<=m/2;i++)
if(m%i==0)
return false;
return true;
}
void DFS(int k){
if(k>n)
return ;
if(j==n){
if(isprime(a[j-1],1)){
for(int l=0;l<j-1;l++)
cout<<a[l]<<" ";
cout<<a[j-1]<<endl;
}
return ;
}
int i;
for(i=1;i<=n;i++)
{
if(!vi[i]&&isprime(k,i)){
a[j++]=i;
vi[i]=1;
DFS(i);
vi[i]=0;
j--;
}
}
}
int main()
{
int count=0,s=0;
while(cin>>n){
cout<<"Case "<<++count<<":"<<endl;
j=0;
memset(vi,0,sizeof(vi));
vi[1]=1;
a[j++]=1;
DFS(1);
cout<<endl;
}
return 0;
}