UVA 10801

#include <bits/stdc++.h>
using namespace std; typedef long long ll; typedef unsigned long long ull; const int mod = 1e9 + 7, N = 1010, inf = INT_MAX;
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define ep emplace_back
//#define int ll

int n, m, ans, c[N], dist[N], visited[N];

signed main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    while (cin >> n >> m)
    {
        ans = inf;
        vector<pair<int, int>>adj[N];
        vector<int>lon[N];
        for (int i = 1; i <= n; i++)
        {
            cin >> c[i];
        }
        for (int a = 0; a <= n; a++)
        {
            string s;
            getline(cin, s);
            stringstream z(s);
            int now, pre;
            z >> pre;
            lon[a].ep(pre);
            while (z >> now)
            {
                lon[a].ep(now);
                adj[a * 100 + pre].ep(100 * a + now, (now - pre)*c[a]);
                adj[a * 100 + now].ep(100 * a + pre, (now - pre)*c[a]);
                pre = now;
            }
        }
        for (int i = 0; i < 100; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                for (int k = 1; k <= n; k++)
                {
                    if (j == k) continue;
                    if (binary_search(lon[j].begin(), lon[j].end(), i)
                        && binary_search(lon[k].begin(), lon[k].end(), i))
                    {
                        adj[100 * j + i].ep(100 * k + i, 60);
                    }
                }
            }
        }
        for (int st = 100; st <= n * 100; st += 100)
        {
            memset(visited, 0, sizeof visited);
            fill(dist, dist + N, inf);
            priority_queue<pair<int, int>>q;
            q.emplace(0, st);
            dist[st] = 0;
            while (!q.empty())
            {
                int s = q.top().se; q.pop();
                if (visited[s]) continue; visited[s] = 1;
                for (auto u : adj[s])
                {
                    if (dist[u.fi] > dist[s] + u.se)
                    {
                        dist[u.fi] = dist[s] + u.se;
                        q.emplace(-dist[u.fi], u.fi);
                    }
                }
            }
            for (int i = 1; i <= n; i++)
            {
                ans = min(ans, dist[100 * i + m]);
            }
        }
        if (ans != inf) cout << ans << endl;
        else cout << "IMPOSSIBLE\n";
    }
}