#include <fstream>

using namespace std;

const char InFile[]="reguli.in";
const char OutFile[]="reguli.out";
const int MaxN=500111;

ifstream fin(InFile);
ofstream fout(OutFile);

int N,sol,ind;
long long V[MaxN];

int main()
{
	fin>>N;
	for(register int i=1;i<=N;++i)
	{
		fin>>V[i];
		V[i-1]=V[i]-V[i-1];
	}
	fin.close();
	
	int ind=1;
	int sol=1;
	for(register int i=2;i<N;++i)
	{
		if(V[ind]==V[i])
		{
			++ind;
			if(ind>sol)
			{
				ind=1;
			}
		}
		else
		{
			sol=i;
			ind=1;
		}
	}
	
	fout<<sol<<"\n";
	for(register int i=1;i<=sol;++i)
	{
		fout<<V[i]<<"\n";
	}
	fout.close();
	return 0;
}