A Spy in the Metro

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <vector>
#include <string>
#include <cctype>
#include <complex>
#include <cassert>
#include <utility>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std;
typedef pair<int,int> PII;
typedef long long ll;
#define lson l,m,rt<<1
#define pi acos(-1.0)
#define rson m+1,r,rt<<11
#define All 1,N,1
#define read freopen("in.txt", "r", stdin)
const ll  INFll = 0x3f3f3f3f3f3f3f3fLL;
const int INF= 0x7ffffff;
const int mod =  1000000007;
int dp[60][210],ld[60][210],rd[60][210];
int n,T,m,t[60];
void solve(){
    memset(dp,0x3f,sizeof(dp));
    dp[n][T]=0;
    for(int j=T-1;j>=0;--j)
        for(int i=1;i<=n;++i)
    {
        dp[i][j]=dp[i][j+1]+1;
        if(ld[i][j])dp[i][j]=min(dp[i][j],dp[i-1][j+t[i-1]]);
        if(rd[i][j])dp[i][j]=min(dp[i][j],dp[i+1][j+t[i]]);
    }
    if(dp[1][0]>T)printf("impossible\n");
    else printf("%d\n",dp[1][0]);
}
int main()
{
    int ca=0;
    while(~scanf("%d",&n)){
        if(n==0)break;
        scanf("%d",&T);
        for(int i=1;i<n;++i)
            scanf("%d",&t[i]);
        int tmp;
        memset(ld,0,sizeof(ld));
        memset(rd,0,sizeof(rd));
         scanf("%d",&m);
        while(m--){
            scanf("%d",&tmp);
            for(int i=1;i<=n;++i)
            {
                rd[i][tmp]=1;
                tmp+=t[i];
            }
        }
        scanf("%d",&m);
        while(m--){
            scanf("%d",&tmp);
            for(int i=n;i>0;--i)
            {
                ld[i][tmp]=1;
                tmp+=t[i-1];
            }
        }
        printf("Case Number %d: ",++ca);
        solve();
    }
return 0;
}