#include <bits/stdc++.h>
using namespace std;

const int N=1026;
int n,m,a[N],b[N];
int dp[2][N],from[2][N];
vector <int> cmlsc;
void rec(int x1,int y1,int x2,int y2)
{
	if(x1>x2||y1>y2)return;
	if(x1==x2)
	{
	    for(int j=y1;j<=y2;++j)
        if(b[j]==a[x1]){
	    cmlsc.push_back(a[x1]);
		return;}
		return;
	}
	int mid=(x1+x2)/2;
	bool l=0;
	memset(dp,0,sizeof dp);
	memset(from,0,sizeof from);
	for(int k=x1; k<=mid; ++k)
	{
		l^=1;
		memset(dp[l],0,sizeof dp[l]);
		for(int j = y1; j <= y2; ++j)
		{
			if(a[k] == b[j])
			{
				dp[l][j] = dp[l ^ 1][j - 1] + 1;
			}
			else
			{
				if(dp[l^1][j]>dp[l][j-1])
					dp[l][j] =dp[l^1][j];
				else dp[l][j]=dp[l][j-1];
			}
		}
	}
	for(int j = y1; j <= y2; ++j) from[l][j] = j;
	for(int k=mid+1; k<=x2; ++k)
	{
		l ^= 1;
		memset(dp[l], 0, sizeof dp[l]);
		memset(from[l], 0, sizeof from[l]);
		for(int j=y1; j<=y2; ++j)
		{
			if(a[k] == b[j])
			{
				dp[l][j] = dp[l ^ 1][j - 1] + 1, from[l][j] = from[l ^ 1][j - 1];
			}
			else
			{
				if(dp[l^1][j]>dp[l][j-1])
					dp[l][j] =dp[l^1][j], from[l][j] = from[l ^ 1][j];
				else dp[l][j]=dp[l][j-1], from[l][j] = from[l][j - 1];
			}
		}
	}
	int val = from[l][y2];
	rec(x1,y1,mid,val);
	rec(mid+1,val+1,x2,y2);

}
int main()
{
	ifstream cin("cmlsc.in");
	ofstream cout("cmlsc.out");
	cin>>n>>m;
	for(int i=1; i<=n; ++i)cin>>a[i];
	for(int i=1; i<=m; ++i)cin>>b[i];
	rec(1,1,n,m);
	cout<<cmlsc.size()<<'\n';
	for(auto it:cmlsc)cout<<it<<' ';
}