1 #include <bits/stdc++.h>
 2 using namespace std;
 3 
 4 const int maxn=50+5,maxt=200+5,INF=0x3fffffff;
 5 int n,T,M1,M2,kase;
 6 int t[maxn],dp[maxt][maxn];
 7 bool has_train[maxt][maxn][2];
 8 
 9 void solve(){
10     for(int i=1;i<=n;i++) dp[T][i]=INF;
11     dp[T][n]=0;
12     for(int i=T-1;i>=0;i--)
13         for(int j=1;j<=n;j++){
14             dp[i][j]=dp[i+1][j]+1;
15             if(j<n&&has_train[i][j][0]&&i+t[j]<=T)
16                 dp[i][j]=min(dp[i][j],dp[i+t[j]][j+1]);
17             if(j>1&&has_train[i][j][1]&&i+t[j-1]<=T)
18                 dp[i][j]=min(dp[i][j],dp[i+t[j-1]][j-1]);
19         }
20     printf("Case Number %d: ",++kase);
21     if(dp[0][1]>=INF) puts("impossible");
22     else printf("%d\n",dp[0][1]);
23 }
24 void init(){
25     scanf("%d",&T);
26     for(int i=1;i<n;i++){
27         scanf("%d",&t[i]);
28     }
29     memset(has_train,0,sizeof has_train);
30     scanf("%d",&M1);
31     for(int i=1;i<=M1;i++){
32         int d; scanf("%d",&d);
33         int station=1;
34         while(d<=T&&station<n){
35             has_train[d][station][0]=true;
36             d+=t[station++];
37         }
38     }
39     scanf("%d",&M2);
40     for(int i=1;i<=M2;i++){
41         int d; scanf("%d",&d);
42         int station=n;
43         while(d<=T&&station>0){
44             has_train[d][station][1]=true;
45             d+=t[station-1]; station--;
46         }
47     }
48 }
49 int main(){
50     while(scanf("%d",&n)&&n){
51         init();
52         solve();
53     }
54     return 0;
55 }