#include <fstream>

using namespace std;
ifstream f("reguli.in");
ofstream g("reguli.out");

int n,i,x,l,a[500005],y,k,p[500005],sol;
int main()
{
   f>>n>>x;
   l=0;
   for(i=2;i<=n;i++)
   {
       f>>y;
       a[++l]=y-x;
       x=y;
   }
   for(i=2;i<=l;i++)
   {
       for(;k!=0&&a[k+1]!=a[i];)k=p[k];
       if(a[k+1]==a[i])k++;
       p[i]=k;
   }
   sol=k-1-p[k-1];
   g<<sol<<'\n';
   for(i=1;i<=sol;i++)g<<a[i]<<'\n';
    return 0;
}