#include <cstdio>
#include <algorithm>
using namespace std;
const int N = 100;
int n, m;
unsigned long long int s, a[N];
bool Find(unsigned long long int t, int p) {
    if(p >= n) return s == (t & s);
    if(Find(t^a[p], p+1)) return 1;
    if(Find(t, p+1)) return 1;
    return 0;
}
int main() {
    freopen("medicine.in", "r", stdin);
    freopen("medicine.out", "w", stdout);
    while(scanf("%d %d", &n, &m) == 2) {
        s = 0;
        int t, r;
        for(int i=0; i<m; i++) {
            scanf("%d", &r);
            s += 1ull << r;
        }
        for(int i=0; i<n; i++) {
            a[i] = 0;
            scanf("%d", &t);
            for(int j=0; j<t; j++) {
                scanf("%d", &r);
                a[i] ^= 1ull << r;
            }
        }
        printf("%sossible\n", Find(0, 0) ? "P" : "Imp");
    }
    return 0;
}