#include<bits/stdc++.h>
using namespace std;
constexpr int M=1005;
int n,m,a[M][M],p[M],tmp[M];
bool vis[M],res[M];vector<int>ans;
int read(){
    int x=0;char ch=getchar();
    while (!isdigit(ch)) ch=getchar();
    while (isdigit(ch)) x=x*10+ch-48,ch=getchar();
    return x;
}
int main(){
    n=read();m=read();
    for (int i=1;i<=m;i++)
        for (int j=1;j<=n;j++)
            a[i][j]=read();
    iota(p+1,p+m+1,1);
    while (1){
        for (int i=1;i<=m;i++)
            for (int j=1;j<=n;j++)
                if (!vis[tmp[i]=a[p[i]][j]]){
                    vis[tmp[i]]=res[tmp[i]]=1;break;
                }
        for (int i=1;i<=m;i++) vis[tmp[i]]=0;
        if (!next_permutation(p+1,p+m+1)) break;
    }
    for (int i=1;i<=n;i++)
        if (res[i]) ans.emplace_back(i);
    printf("%d\n",(int)ans.size());
    for (auto x:ans) printf("%d ",x);puts("");
    return 0;
}