#include <bits/stdc++.h>

int m, n;
int pos[11][1003];
bool ok[1003], used[1003], vis[11];

void gen(int k) {
    if (k == m) return;
    for (int i = 0; i < m; i++)
    if (!vis[i]) {
        vis[i] = 1;
        for (int j = 1; ; j++) {
            const int x = pos[i][j];
            if (!used[x]) {
                used[x] = 1;
                ok[x] = 1;
                gen(k + 1);
                used[x] = 0;
                break;
            }
        }
        vis[i] = false;
    }
}

int main() {
    scanf("%d%d", &n, &m);
    for (int i = 0; i < m; i++)
    for (int j = 1; j <= n; j++)
        scanf("%d", &pos[i][j]);
    gen(0);
    int cnt = 0;
    for (int j = 1; j <= n; j++) cnt += ok[j];
    printf("%d\n", cnt);
    for (int j = 1; j <= n; j++)
        if (ok[j])
            printf("%d ", j);
    return 0;
}