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OI-codes/Luogu/CF1166E/CF1166E.cpp

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#include <iostream>
#include <bitset>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 1e4 + 5;
int m, n;
std::bitset<N> s[55];
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> m >> n;
for (int i = 1, k; i <= m; i++) {
cin >> k;
for (int j = 1, x; j <= k; j++) {
cin >> x;
s[i].set(x);
}
for (int j = 1; j < i; j++) {
if (!(s[i] & s[j]).count()) {
cout << "impossible" << endl;
exit(0);
}
}
}
cout << "possible" << endl;
return 0;
}