#include<fstream>
#include<vector>
std::ifstream fin("cmlsc.in");
std::ofstream fout("cmlsc.out");
int mat[1024][1024];
int v1[1024], v2[1024];
void read(int &n, int &m)
{
    fin>>n>>m;
    for(int index=0; index<n; ++index)
        fin>>v1[index];
    for(int index=0; index<m; ++index)
        fin>>v2[index];
}
void createMatrix(int n, int m)
{
    for(int index=1; index<=n; ++index)
        for(int next=1; next<=m; ++next)
            mat[index][next]=std::max(std::max(mat[index-1][next], mat[index][next-1]), mat[index-1][next-1]+(v1[index-1]==v2[next-1]));
    fout<<mat[n][m]<<'\n';
}
void findAns(int i, int j, int local)
{
    if(local==0)
        return;
    if(mat[i-1][j]>mat[i][j-1])
        findAns(i-1, j, mat[i-1][j]);
    else
        findAns(i, j-1, mat[i][j-1]);
    if(v1[i-1]==v2[j-1])
        fout<<v1[i-1]<<" ";
}
int main()
{
    int n, m;
    read(n, m);
    createMatrix(n, m);
    findAns(n, m, mat[n][m]);
    fin.close();
    fout.close();
    return 0;
}