#include<cstdio>
int v[1025],d,s[1025][1025],i,j,n,m,x[1025],y[1025],k,e;
int main()
{freopen("cmlsc.in","r",stdin);
freopen("cmlsc.out","w",stdout);
scanf("%d%d",&n,&m);
for(i=1;i<=n;i++)
      scanf("%d",&x[i]);
for(i=1;i<=m;i++)
      scanf("%d",&y[i]);
for(i=1;i<=n;i++)
for(j=1;j<=m;j++)
      {s[i][j]=s[i-1][j-1]+(x[i]==y[j]);
      if(s[i][j]<s[i-1][j])
             s[i][j]=s[i-1][j];
      if(s[i][j]<s[i][j-1])
             s[i][j]=s[i][j-1];}
printf("%d\n",s[n][m]);
k=s[n][m];
for(i=n;i;i--)
for(j=m;j;j--)
if(s[i][j]==k)
      v[k]=y[j],d=i-1,e=j-1;
for(i=k-1;i;i--)
      {while(s[d-1][e]==i)
             d--;
      while(s[d][e-1]==i)
             e--;
      v[i]=x[d],d--,e--;}
for(i=1;i<=k;i++)
      printf("%d ",v[i]);             
return 0;}