#include <bits/stdc++.h>
#define DMAX 1026

using namespace std;

ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");

int n,m,i,j;
int a[DMAX];
int b[DMAX];
int lgmax[DMAX][DMAX];
int unde[DMAX][DMAX];

int main()
{
 //citire
 fin>>n>>m;
 for (i=1;i<=n;i++)
  fin>>a[i];
 for (i=1;i<=m;i++)
  fin>>b[i];
 for (i=n;i>0;i--)
  for (j=m;j>0;j--)
 {
  if (a[i]==b[j])
  {
   lgmax[i][j]=1+lgmax[i+1][j+1];
   unde[i][j]=1;
  }
  else
  {
   if (lgmax[i+1][j]>lgmax[i][j+1])
   {
    lgmax[i][j]=lgmax[i+1][j];
    unde[i][j]=2;
   }
   else
   {
    lgmax[i][j]=lgmax[i][j+1];
    unde[i][j]=3;
   }
  }
 }
 fout<<lgmax[1][1]<<"\n";
 i=1;
 j=1;
 while (i<=n&&j<=m)
 {
  if (unde[i][j]==1)
  {
   fout<<a[i]<<" ";
   i++;
   j++;
  }
  else
  {
   if (unde[i][j]==2)
    i++;
   else
    j++;
  }
 }
 fout<<"\n";
 fout.close();
 return 0;
}