#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");
int c[1025][1025],a[1025],b[1025],v[1025],n,m;
int main()
{
    fin>>n>>m;
    for(int i=1;i<=n;i++)
        fin>>a[i];
    for(int i=1;i<=m;i++)
        fin>>b[i];
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
        {
            if(c[i][j-1]>=c[i-1][j]&&c[i][j-1]>=c[i-1][j-1])
                    {
                        if(a[i]==b[j])
                        {
                            c[i][j]=c[i][j-1]+1;
                        }
                        else c[i][j]=c[i][j-1];

                    }
                else if(c[i][j]<=c[i-1][j]&&c[i-1][j]>=c[i-1][j-1])
                        {
                             if(a[i]==b[j])
                            {
                                c[i][j]=c[i-1][j]+1;
                            }
                            else c[i][j]=c[i-1][j];

                        }
                   /* else if(c[i-1][j-1]>=c[i-1][j]&&c[i-1][j-1]>=c[i][j-1])
                            {
                                if(a[i]==b[j])
                                {
                                    c[i][j]=c[i-1][j-1]+1;
                                }
                                else  c[i][j]=c[i-1][j-1];
                            }*/
        }

        fout<<c[n][m]<<'\n';

        int i=n,j=m,k=1;

        while((i>=0&&j>=0)&&c[i][j]!=0)
        {
            if(c[i][j-1]!=c[i][j])
            {
                v[k]=a[i];
                k++;
                i=i-1;
                cout<<i+1<<" "<<j<<" "<<c[i+1][j]<<'\n';
            }
            else if(c[i-1][j]!=c[i][j]-1){i--;
            cout<<i+1<<" "<<j<<'\n';
            }
            else {j--;
            cout<<i<<" "<<j+1<<'\n';
            }
        }
        for(int i=k-1;i>=1;i--)
            fout<<v[i]<<" ";
    return 0;
}