#include<bits/stdc++.h>
using namespace std;
int main()
{
int n,i;
cin>>n;
int a[n],b[n];
for(i=0;i<n;i++)
cin>>a[i];
b[0] = 1;
b[1] = 2;
int max = 2;
int dem = 0;
for(i=2;i<n;i++)
{
b[i]=1;
if(a[i]-a[i-1]==a[i-1]-a[i-2])
b[i] += b[i-1];
else b[i]++;
if(b[i]>max)
{
max = b[i];
dem = 1;
}
else if(b[i]==max) dem++;
}
cout<<dem<<"\n";
for(i=n-1;i>0;i--)
{
if(b[i]==max)
{
for(int j=max;j>0;j--)
cout<<a[i-j+1]<<" ";
cout<<"\n";
}
}
}
