#include <fstream>

using namespace std;
ifstream f("cmlsc.in");
ofstream g("cmlsc.out");
int b[1025], c[1025], m, n, i, j,x=0, a[1025][1025], sub[1025];
int main()
{
    f >> n >> m ;
    for( i = 1 ; i <= n ; i++ )
        f >> b[i];
    for( j = 1 ; j <= m ; j++ )
        f >> c[j];
    for( i = 1 ; i <= n ; i++ )
    {
        for( j = 1 ; j <= m ; j++ )
        {
             if( b[i] == c[i] )
                a[i][j] = a[i-1][j]+1;
             else
                a[i][j] = max( a[i-1][j] , a[i][j-1]);
        }
    }
    i = n, j = m ;
    while( a[i][j] )
    {
         if( a[i][j] == a[i-1][j] )
            i--;
         if( a[i][j] == a[i][j-1] )
            j--;
         x++;
         sub[x] = b[i];
         i--, j--;
    }
    g << a[n][m]<<"\n";
    for(i=x ; i>=1 ; i--)
        g << sub[i] <<" ";
    return 0;
}