#include <bits/stdc++.h>

#ifdef LOCAL
#include <debug.h>
#else
#define debug(...)
#define debug_arr(...)
#define debug_endl(...)
#endif

void solve() {
	int n, m;
	std::cin >> n >> m;

	std::vector p(m, std::vector<int>(n));
	for (int i = 0; i < m; i++) {
		for (int j = 0; j < n; j++) {
			std::cin >> p[i][j];
			p[i][j]--;
		}
	}

	std::vector vis(n, false), ans(n, false);
	std::vector<int> o(m);
	std::iota(o.begin(), o.end(), 0);

	do {
		std::vector<int> a(m);
		for (int i : o) {
			a[i] = *std::ranges::find_if(p[i], [&](int x) -> bool {
				return !vis[x];
			});
			vis[a[i]] = ans[a[i]] = true;
		}
		for (int i = 0; i < m; i++) {
			vis[a[i]] = false;
		}
	} while (std::next_permutation(o.begin(), o.end()));

	std::cout << std::ranges::count(ans, true) << "\n";
	for (int i = 0; i < n; i++) {
		if (ans[i]) {
			std::cout << i + 1 << " ";
		}
	}
	std::cout << "\n";
}

int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	std::cout.setf(std::ios::fixed);
	std::cout.precision(10);

	solve();

	return 0;
}