#include <bits/stdc++.h>
using namespace std;

#define all(x) begin(x), end(x)
#define sz(x) (ll)(x).size()

using ll = long long;
using ld = long double;

constexpr ll MOD = 1'000'003;
vector<ll> inv(MOD);

ll n, r;
vector<vector<ll>> in, adj, mat;
mt19937 rng(1234567890);

constexpr ll powMod(ll a, ll b, ll n) {
	ll res = 1;
	while (b > 0) {
		if (b & 1) res = (a * res) % n;
		a = (a * a) % n;
		b /= 2;
	}
	return res;
}

void normalLine(int line) {
	ll factor = inv[mat[line][line]];
	for (ll& x : mat[line]) x = (x * factor) % MOD;
}

void takeAll(int n, int line) {
	for (int i = 0; i < n; i++) {
		if (i == line) continue;
		ll diff = mat[i][line];
		for (int j = 0; j < n; j++) {
			mat[i][j] -= (diff * mat[line][j]) % MOD;
			mat[i][j] = (mat[i][j] + MOD) % MOD;
}}}

bool gauss(int n) {
	vector<bool> done(n, false);
	for (int i = 0; i < n; i++) {
		int j = 0;
		while (j < n && (done[j] || mat[j][i] == 0)) j++;
		if (j == n) return false;
		swap(mat[i], mat[j]);
		normalLine(i);
		takeAll(n, i);
		done[i] = true;
	}
	return true;
}

bool solve() {
	uniform_int_distribution<ll> dist(1, MOD);
	mat.assign(2*n, vector<ll>(2*n));
	for (ll i = 0; i < 2*n; i++) {
		for (ll j = i+1; j < 2*n; j++) {
			bool skip = false;
			for (ll k = 0; k < r && !skip; k++) {
				skip |= (in[k][i] > n) == (in[k][j] > n);
			}
			if (!skip) {
				mat[i][j] = dist(rng);
				mat[j][i] = MOD - mat[i][j];
			}
		}
	}
	return gauss(2*n);
}

int main(int argc, char *argv[]) {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	for (ll i = 1; i < MOD; i++) inv[i] = powMod(i, MOD - 2, MOD);

	cin >> n >> r;
	in.assign(r, vector<ll>(2*n));
	for (auto& v : in) {
		for (auto& x : v) cin >> x;
	}
	if (!solve()) cout << "im";
	cout << "possible" << endl;
}