#include<fstream>
using namespace std;
// declarations
const int LEN = 1025;
int N,M,a[LEN],b[LEN], mat[LEN][LEN],sol[LEN];

int check(int x, int y){
    return (x > y) ? x : y;
}
int cmlsc(int &k){
    for(int i = 1; i <= N; i++){
        for(int j = 1; j <= M; j++){
            if(a[i-1] == b[j-1]){
                mat[i][j] = mat[i-1][j-1]+1;
                sol[k] = a[i-1];
                k++;
            }
            else mat[i][j] = check(mat[i][j-1], mat[i-1][j]);
        }
    }
    return mat[N][M];
}
int main()
{
    int i,len = 0;
    ifstream fin("cmlsc.in");
    ofstream fout("cmlsc.out");
    fin >> N >> M;
    for(i = 0; i < N; i++){
        fin >> a[i];
        mat[i][0] = 0;
    }
    for(i = 0; i < M; i++){
        fin >> b[i];
        mat[0][i] = 0;
    }
    fout << cmlsc(len)<<"\n";
    for(i = 0; i < len; i++){
        fout << sol[i] << " ";
    }
    fout <<"\n";
    fin.close();
    fout.close();
    return 0;
}