#include <fstream>
using namespace std;

ifstream cin("reguli.in");
ofstream cout("reguli.out");

int v[500005];
int n, b, a, ans, k;

int main()
{
    cin >> n >> b;
    for(int i = 1; i < n; i++)
    {
        cin >> a;
        v[i] = a - b;
        b = a;
    }
    int k = 2;
    while(v[k] != v[1])
    {
        k++;
    }
    ans += k - 1;
    for(int i = k + 1; i < n; i++)
    {
        if(v[i] != v[i - k + 1])
        {
            ans++;
            k++;
        }
    }
    for (int i = 1; i < n - ans; ++i)
        if (v[i] != v[i + ans])
            ans = n - 1;
    cout << ans << '\n';
    for(int i = 1; i <= ans; i++)
    {
        cout << v[i];
        cout << '\n';
    }
    return 0;
}